There is no final puzzle we could solve to get a handle on reality. — Agent Smith

Sounds like Gödel's incompleteness theorem.

For example I think until we understand consciousness we cannot possibly know the true nature of reality or whether the contents of consciousness are veridical.........I have had solipsistic intuitions/feelings in the past. I think we need to defeat solipsism or face a kind of personal isolation where we are able to be skeptical about everything but cogito ergo sum/ourselves. — Andrew4Handel

Solipsism, consciousness and the problem of cause and effect

I am conscious of the colour red, taste something sweet, feel something smooth, hear a slight crackle and smell something fruity. I know these sensations, and believe they have been caused by the apple in front of me.

Solipsism is the position that the consciousness of these sensations certainly exist in the mind and have been caused by the mind itself rather than anything external to the mind. My belief that solipsism is not true is the same reason that I believe consciousness can never be understood, and relates to the problem of cause and effect.

If solipsism were true, then I created everything that I know, such that I created the novels War and Peace, Don Quixote, all the compositions of Bach and Mozart, all the paintings by Derain and Van Gogh, all the scientific discoveries of Feynman and Einstein, etc. As I have difficulty winning at chess, I find it hard to believe that I have such godlike powers.

According to Newton's first law of motion, a stationary object cannot move unless it is acted upon an external force. The Principle of Sufficient Reason, a term coined by Leibniz, and central to Spinoza's philosophical system states that every fact has a reason for obtaining and there are no "brute facts". If something existed for no reason, then the fact it existed would be inexplicable. Aristotle claimed that a person when perceiving anything must also perceive their own existence, suggesting that consciousness entails self-consciousness. However, Schopenhauer wrote, in agreement with Kant, “that the subject should become an object for itself is the most monstrous contradiction ever thought of”. As an object cannot spontaneously cause itself to move in the absence of an external force, a conscious thought cannot spontaneous cause itself to come into existence in the absence of an external cause. Colin McGinn has said that consciousness is "a mystery that human intelligence will never unravel", in that no matter how much scientists study the brain, the mind is fundamentally incapable of comprehending itself, a position called New Mysterianism.

If the concept of cause and effect is fundamental to our beliefs, it follows that not only that Solipsism is not true but we will never be able to understand consciousness.

So if I were to say " An "insoluble puzzle" is not really a puzzle" what could I mean to say beyond "Calling an "insoluble puzzle" a puzzle is not the most useful way to talk about it"? — Janus

Perhaps the bigger puzzle is how do we decide whether a puzzle, such as the puzzle of consciousness, is an impossible puzzle or not.

Does an insoluble puzzle count as a puzzle at all? — Janus

It must do, in the same way that there are impossible problems and impossible objects.

Wikipedia even has a list of impossible puzzles.

War between peoples has always been an impossible problem. If an impossible problem didn't count as a problem, then it would follow that war between peoples is not a problem.

I could say that there is an object on the table in front of me that is round and square. If this impossible round square object didn't count as an object, then how could I refer to the object that is on the table in front of me.

In language, there are impossible puzzles, impossible problems and impossible objects.

Why are we able to understand reality at all? — Andrew4Handel

The world appears logically consistent, which allows us, for example, to use Newton's second law F = m * a to predict future events. But does being able to predict what will happen mean that we understand why it will happen. We may know F = m * a, but do we understand why F = m * a ?

To me existence is a puzzle. — Andrew4Handel

As with Windows Free Cell game 11,982, some puzzles are insoluble. Why should we think that all puzzles are soluble.

The alien, the human and the donkey

Life first started to evolve on Earth about 3.5 billion years ago, and there is no reason to think it has stopped.

We can show a donkey, which has a certain level of intelligence, the novel The Old Man and the Sea by Hemingway and not expect the donkey to understand the plot-line. No amount of patient explanation or education will enable the donkey our level of understanding.

An alien, having several million years of further evolution, will have their own knowledge and understanding. The alien can show the human some of their knowledge and understanding and quite reasonably not expect the human to understand. No amount of patient explanation or education by the alien will enable the human their level of understanding. As we have knowledge and understanding the donkey can never have, the alien will have knowledge and understanding we can never have.

It is not so much our fallibilism, in that our knowledge might turn out to be false, but rather, as has been said before, the unknown unknown, facts in the world that we are incapable of ever understanding even if staring us in the face.

Our capacity to understand is itself something of a mystery. — Andrew4Handel

If understanding is knowledge about a subject, our understanding and knowledge can only go so far, until reaching an inevitable barrier beyond which they cannot pass. There is no topic that does not hit such a barrier beyond which is unknown and not understood.

We can infer what will happen through observing constant conjunctions, that because the sun rose in the east for the previous 100 days there is the inference that tomorrow it will also rise in the east, but this does not mean that we understand why the sun will rise in the east tomorrow.

We may understand and know the rules of algebra, such that 5 * 3 + 2 = 17 whilst 5 * (3 + 2) = 25, or we may understand the rules of language, in order to know when someone says "that's OK", whether they are praising me, criticizing me, expressing exasperation with me, encouraging me, or even saying you’re disgusted with me. Yet such understanding and knowledge is founded on rules that we must accept and not question if wanting to keep on playing the social game.

Beyond the knowable is the unknown, which can only understand in terms of metaphor, figure of speech, myth, parable, fable, etc.

All our understanding and knowledge is thereby founded on metaphor, figure of speech, myth, parable, fable, etc.

What does it mean to solve the puzzle of consciousness. In what sense can we ever understand consciousness. In what sense do we understand anything. How do we understand what it is to understand. What do we think we understand and how do we understand them.

For example, as regards science it is said we understand the following: Big Bang Theory, Hubble's Law of Cosmic Expansion, Kepler's Laws of Planetary Motion, Universal Law of Gravitation, Newton's Laws of Motion, Laws of Thermodynamics, Archimedes' Buoyancy Principle, Evolution and Natural Selection, Theory of General Relativity and Heisenberg's Uncertainty Principle. Yet such understanding is metaphorical, in that we understand the start of the universe as a "big bang", something we have experience of in our daily lives, whether fireworks, an explosion or a door slamming.

As regards society, it is said we have a good understand of the following: government, religion, education, economy, language, politics, culture, ethnicity, gender and recreation. Yet such understanding is of concepts that only exist in the mind, in that governments don't exist in a mind-independent world.

Our understanding is therefore based on either metaphor which only exist in the mind or concepts which again only exist in the mind. Even if we did better understand consciousness, such understanding can only ever be a better understanding of the concepts existing in our mind and can never be an understanding of what in a mind-independent world caused these concepts in the mind.

So, to better understand the nature of consciousness, the best we can do is look for better metaphors to explain it. The Truth only exists in language.

If these puzzles are ultimately insoluble by humans, then why not also add "World Peace" to the list.

What are the biggest puzzles in philosophy to you? — Andrew4Handel

Another puzzle, perhaps overriding all of these, is why it is believed that humans will ever be capable of solving these puzzles.

What reason is given that humans will ever be able to solve these puzzles.

So, why nit-pick what he may have really meant or thought — Vera Mont

Because this thread was initiated asking the question whether Descartes was an "evil genius", which can only be about what he meant or thought.

I see the physic this relation of the modern rationalist being antagonized by the irrational, and the symbolic nature of a human bein violent towards a dog with the added layer of scientism, as an important message. — introbert

Are you saying that, even though Descartes didn't, in fact, torture dogs, the myth that Descartes did torture dogs has a value as a symbol that sends an important message to society, and, as a myth, is something that only the rationalist would object to?

From the magazine "Philosophy Now", within the article by Samuel Kaldas titled Descartes versus Cudworth On The Moral Worth of Animals is written: "Descartes undeniably did set up a strict dichotomy between the immaterial, experiencing, thinking life of man, and the material, mechanical, mindless existence of animals. That dichotomy certainly doesn’t encourage any sense of kinship between man and beast."

Is it true that Descartes set up a strict dichotomy between the thinking life of humans and the mindless existence of animals?

Not according to John Cottingham is his article "A Brute to the Brutes?": Descartes' Treatment of Animals". He writes "To be able to believe that a dog with a broken paw is not really in pain when it whimpers is a quite extraordinary achievement even for a philosopher." and "Now from none of all this does it follow that when Descartes calls some- thing a 'mechanism' or 'machine' he is automatically ruling out the presence of sensations or feelings". He concludes "At the end of the day, Descartes may not have been completely consistent, but at least he was not altogether beastly to the beasts"

Is it true that even if there was a strict dichotomy between animals and humans, as the author writes, there could be no sense of kinship?

From John Cottingham's measured argument, we can conclude that not only for Descartes but philosophers today, feeling and sensation is not part of any dichotomy between animals and humans.

Yet today many believe that only humans have the ability to reason, whilst animals are driven solely by instinct, though not an opinion I share. Even if this dichotomy between instinct and reason was true, it clearly doesn't in practice preclude any sense of kinship between humans and animals, in that even amongst those who believe in this dichotomy, there is still a sense of kinship with animals either as pets or in the natural world.

IE, the paragraph in "Philosophy Now" is according to John Cottingham's argument not only mistaken in its critique of Descartes but also in its conclusion that a sense of kinship cannot override any dichotomy (whether it exists or not) between animals and humans.

Where is that from? I know Peter Harrison's work, I'd be interested in following up on that. — Wayfarer

The Philosophical Quarterly Vol 42 No 167 April 1992 "Descartes on Animals" Peter Harrison - www.jstor.org/stable/2220217

Peter Harrison remarks that John Cottingham has suggested that the passages in the Cartesian corpus don't support the common view that Descartes denied feeling to animals. As also mentioned by the SEP on Rene Descartes, which refers to Harrison and Hatfield. See also Chapter X "Descartes' Treatment of Animals" of John Cottingham's book Descartes (which I cannot find online).

Criticism is not cancellation! In fact the inability to make this distinction is one of the primary drivers of 'cancel culture'. — Wayfarer

Totally agree.

Quite what Descartes means by 'thought', why humans have it and animals don't — Wayfarer

I don't believe that there was a sharp cut-off between animals and humans as regards intelligence, feelings, reasoning, propositional attitudes, etc, but there was a gradual evolutionary process over millions of years. After all, humans are animals. For me, a dog has the same "quality" of reasoning as a human, even if the "quantity" is less. There are many examples where the behaviour of certain animals seems to clearly show that they are reasoning through a problem, and thereby have propositional l attitudes.

However, some disagree. For example, Donald Davidson denies that animals have propositional attitudes, though doesn't deny that they have no mental life at all.

The problem with treating animals as being of a different kind to ourselves is the consequence that we may treat animals inhumanely.

Where do they come from? — Vera Mont

The sentence from the Britannica: "He argued that, because animals have no souls, they do not think or feel; thus, vivisection, which Descartes practised, is permitted" gives a different impression to the OP whereby "They burned, scalded, and mutilated animals in every conceivable manner".

As vivisection is still legal, can we attack Descartes for a practice that is still carried out today.

Peter Harrison writes "The view that Descartes was a brute to the brutes is, above all else, historically myopic" and "Descartes is commonly portrayed as one whose view of animals is morally repugnant. Such moral indignation is misplaced".

Descartes position regarding the soul is more complex that suggested by The Britannica. The Britannica writes "He argued that, because animals have no souls, they do not think or feel", however Peter Harrison writes " Descartes, we must understand, did not deny the existence of animal souls per se: animals might well have "corporeal souls". It was this view that animals had spiritual souls, of "substantial material forms" that Descartes was at pains to refute".

Before cancelling Descartes and tearing down his statues, I think first the truth should be discovered regarding his position on animal testing.

Then we can judge him having 400 years of hindsight.

How about by the constant standards of cultures that understood the evident kinship of humans and other animals long before gentlemen in stiff collars cerebrated that radical idea? — Vera Mont

It seems a pity that the father of modern philosophy is being discredited for something he probably never did.

In the article Descartes on Animals in the Philosophical Quarterly, Peter Harrison argues that the view that Descartes denied feelings to animals is mistaken.

Apparently Descartes had a pet dog called Monsieur Grat who used to accompany him on his walks, on whom he lavished much affection and probably loved quite dearly.

As Descartes's philosophical starting point was to consider everything a matter of doubt, we should perhaps start by doubting unsubstantiated stories about the man himself.

Well talking to orchids sure is preferable to torturing dogs, I’ll give you that. — Wayfarer

True, in that talking to dogs is preferable to torturing plants.

Descartes reasoned that as animals didn't speak or philosophise, they lacked souls and minds and so were mechanical objects that didn't feel pain. With 400 years of hindsight and accumulated knowledge, today's prevailing view is that animals are not mechanical objects and do feel pain.

Today, the prevailing view is that as plants don't speak or philosophise they lack souls and minds, and so are biologically mechanical objects that don't feel pain. In 400 years from now, in a possible future world, the prevailing view may be that plants are more than biologically mechanical objects and do feel pain.

Is it right that today vegans in eating plants should be judged evil, in the event that in a possible future world, and after 400 years of accumulated knowledge, the prevailing view may be that plants are more than biologically mechanical objects and do feel pain.

Perhaps we could all become Jains — Wayfarer

Or, as an article in The Guardian newspaper proposes, perhaps we should talk to our plants rather than, as the vegans propose, eat them.

"As we edge into 2021, my orchid is still thriving. And because my fingers are not yet green, I can only attribute this to our daily interactions: the adoring looks, the greetings and check-ins, and the attention (both intentional and incidental). She listens in on my telephone conversations and is often my only audience for pre-dinner renditions of I Will Survive. She doesn’t join in, my orchid, but I think she’s feeling the love. I know I am."

If it is right to judge the morality of a philosopher writing 400 years ago by today's standards, then we should expect the morality of philosophers writing today to be judged by the standards of societies 400 years from now.

For example, in a possible future world, it may well be accepted that plants feel pain and should not be picked and eaten whilst still alive. Not an unlikely scenario, as many people discuss this situation even today. That well known left-wing and progressive newspaper The Guardian included the following in its notes and queries section: "A number of studies have shown that plants feel pain, and vegetables are picked and often eaten while still alive. Animal rights activists are often in the news, but has anyone ever protested for vegetable rights?"

This raises the question whether veganism should be promoted today if in a possible future world the eating of plants is considered by society to be morally reprehensible.

Science is about knowing what is true in the world. Philosophy is about doubting what is known to be true in the world.

A crying dog, Descartes maintained, is no different from a whining gear that needs oil — Wayfarer

If you believe that someone is acting immorally, yet they believe that they aren't, in the absence of an ultimate arbiter of morality, why should your opinion outweigh theirs ?

Personally, I believe that animals are intelligent, can reason, feel pain, experience emotions and have propositional attitudes, though not everyone agrees.

Of course heat exists in a body and moves from one object to another, quite literally — Banno

"Water is H₂O" is another unfortunate example where Kripke takes a "holiday" with language. — Richard B

I agree with @Richard B.

Kripke also wrote: “Heat is the motion of molecules.”

Wikipedia - Heat
A thermodynamic system does not contain heat.

www.britannica.com/science/heat
It is incorrect to speak of the heat in a body, because heat is restricted to energy being transferred. Energy stored in a body is not heat

www.quora.com/Does-heat-exist-or-is-it-just-another-defined-quantity-like-energy
Mark Barton - PhD physicist with University of Glasgow
"Heat" is a noun and is spoken of as a substance, even in technical language, but it's a misnomer. Strictly heat doesn't exist, it happens: it's the process of energy moving from one system to another via random microscopic interactions.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html
Heat may be defined as energy in transit from a high temperature object to a lower temperature object. An object does not possess "heat"; the appropriate term for the microscopic energy in an object is internal energy. In warning teachers and students alike about the pitfalls of misusing the word "heat", Mark Zemansky advises: Don't refer to the "heat in a body", or say "this object has twice as much heat as that body".

https://van.physics.illinois.edu/ask/listing/1838
In formal scientific usage, ’heat’ refers not to the total amount of that thermal energy but only to the transfer of thermal energy caused by a temperature difference between objects.

https://www.khanacademy.org/science/chemistry/thermodynamics-chemistry/internal-energy-sal/a/heat
In thermodynamics, heat has a very specific meaning that is different from how we might use the word in everyday speech
Scientists define heat as thermal energy transferred between two systems at different temperatures that come in contact.
We don't talk about a cup of coffee containing heat, but we can talk about the heat transferred from the cup of hot coffee to your hand.
When the two systems are in contact, heat will be transferred through molecular collisions from the hotter system to the cooler system.

https://www.thermal-engineering.org/what-is-heat-in-physics-heat-definition/
While internal energy refers to the total energy of all the molecules within the object, heat is the amount of energy flowing from one body to another spontaneously due to their temperature difference. Heat is a form of energy, but it is energy in transit. Heat is not a property of a system. However, the transfer of energy as heat occurs at the molecular level as a result of a temperature difference.

Heat is a measurement, as is height, number, weight, etc. They don't exist independently of what they are measuring.

If there are two heaps of sand and we move sand from A to B, such that the height of A has decreased and the height of B increased, we don't say that height has literally moved from A to B.
If there are two piles of books and we move four books from A to B, such that the number of books in A has reduced and the number of books in B has increased, we don't say that the number four has literally moved from A to B.
If there are two buckets of water, and we move water from A to B, such that the weight of A has decreased and the weight of B has increased, we don't say that weight has literally moved from A to B.

Similarly, If there are two bodies and energy is transferred from A to B, such that the internal energy of A has decreased and the internal energy of B has increased, we cannot say that heat has literally moved from A to B.

Even if we say something like "the essential properties of this particular lectern are...", all we are doing is making "this particular lectern" into a type. That is because "essential properties" is what defines a type. — Metaphysician Undercover

If "this lectern" is a type, and as types are usually thought to be universals, who is correct, the Realist, the Nominalist or the Conceptualist ?

The Realist thinking that "this lectern" exists in a mind-independent world, the Nominalist who believes that "this lectern" only exists as one particular instantiation at one moment in time or the Conceptualist who understands "this lectern" as a concept existing in the mind only.

It seems Kripke's form of Realism was more linguistic. The reference of "this lectern" is fixed by an act of "initial baptism" which designates a very real physical object with an observable property, such as "this lectern is made of wood". However, the meaning of this expression can evolve over time and even change completely, but what establishes the reality of the expression "this lectern is made of wood" is the existence of a continuous causal chain linked to the initial baptism. Language maintains its stability, even if the meaning of the expressions it uses change with time.

IE, for Kripke's causal theory, expressions within language may start by corresponding with the world, but as time goes by, may correspond less with what initially baptised them as long as they maintain a coherence within the linguistic contexts within which they are used.

When the object "requires a new description", it is because it has changed, therefore it's not "at the same time". It's not at the same time, it's over a duration of time. A thing changes, yet continues to be the same thing, therefore it has contradicting properties, but not at the same time. — Metaphysician Undercover

It depends of which properties are essential for an object to be the same object.

It it is judged that location is an essential property of an object, then if the object changes location then by definition the object has changed. For example, a 1.5m tall piece of wood in a lecture room is a lectern, on a bonfire it is kindling.

If it is judged that location is not an essential property of an object, if the object changes location then by definition it is still the same object. For example, a euro coin in Brussels is money, in Athens it is still money.

No definition is correct, no choice of essential property is correct, as they are based on human judgement. Kripke's rigid designators are also matters of personal judgement.

The amount of heat gained or lost by a sample (q) can be calculated using the equation q = mcΔT, where m is the mass of the sample, c is the specific heat, and ΔT is the temperature change. — Khan

The heat moves from one body to the other, in a process that can be described with mathematical predictability. Nothing metaphorical about it. — Banno

The question is to what extent is scientific language literal or metaphorical. To what extent is Kripke's language literal or metaphorical.

I believe "move" is being used as a figure of speech, not that heat literally moves.

You are by-passing the question as to in what sense does heat, which doesn't exist in a body, and is a measurement, move from one body to another ?

Permit me to take a stab at that. Properties 1. Essential i.e. critical to identity e.g. the 3 sides + the 3 angles of a triangle. 2. Incidental i.e. not critical to identity e.g. the color of the triangle above. — Agent Smith

There are objects in the world and there are "objects" in the mind

Assume in the world is something that has a set of properties: being in a flat plane, three straight sides, having three angles, 10cm large, colour green, rotated at 45 degrees, located in Paris, made of paper, makes no sound, has no smell, etc

What determines that some of these properties are essential to the identity of this something and some properties are incidental ? A mind-independent world cannot make this determination, it can only be made by a person. However, in the event that one person judges that colour is an essential property whilst another person judges that colour is an incidental property, how is it determined who is correct ?

If it is a person who is judging which properties are essential and which incidental, then they are not referring to something that exists in the world as a set of properties, but they are referring to something that exists in the mind as a concept.

I agree that concepts in the mind maintain their identity even though different instantiations of the concept in the world may be associated with different properties.

When object A requires a new description (because it's properties change due to the passing of time), this does not mean that it has become a different object. That's the very reason for the law of identity, to allow us to say that a thing maintains its identity as the same thing, which it is, despite changing as time passes. — Metaphysician Undercover

A person can maintain their identity as the same thing yet at the same time have different properties.

But how can an object maintain its identity as the same thing yet at the same time have different properties ?

Are you content with this account? Is the property of having writ that post essential to your being who you are? Might you not have written it, yet have remained RussellA? — Banno

Yes. I'm not saying that I have Dissociative Identity Disorder, but there are two distinct RussellA's.

There is the RussellA that exists in the world as fundamental particles and forces, and whose identity is constantly changing. At each moment in time, RussellA's properties are both necessary and essential in order for RussellA to be identical with itself. Even if RussellA loses only one fundamental particle, then RussellA's identity would have changed

There is also the "RussellA" that exists on this Forum and whose identity stays the same over time. A "RussellA" that exists in society, exists in the mind and exists in language. "RussellA" has what Kripke calls rigid designators, ensuring that "RussellA's" identity remains the same even in all possible worlds. "RussellA" has necessary and essential properties. What these are no one knows for certain, but I believe that I have them, even if I don't know what they are. I might have had to go shopping, not had time to write this post, yet remained "RussellA". However, RussellA would inevitably have changed, gained weight, lost some more hair, etc.

If I had not written this post, I would still be "RussellA" but I wouldn't be RussellA.

The heat moves from one body to the other, in a process that can be described with mathematical predictability. — Banno

I don't see what relevance this has to the topic, unless you are claiming that the motion of molecules causes heat. — Banno

I agree that Kripke has put forward his case that true identity statements are necessary before introducing the examples of names, heat and my pain. However, if the examples he uses of true necessary identity statements are not in fact true necessary identity statements, then this casts doubt on the case he has previously made.

For example, he is using the word "heat" in two different ways, and when he writes "heat is the motion of molecules", it is unclear in what sense he is using the word "heat". "Heat" can refer to the cause and "heat" can also refer to the effect.

Specifically, Kripke gives an example of a true necessary identity statement as "heat is the motion of molecules"

Heat is the transfer of energy between objects due to a temperature difference between them. Bodies don't contain heat.

Problem one - as regards heat transfer by convection, a body having internal energy moves from location A to location B. As bodies don't contain heat, how can heat be the motion of molecules ?

Problem two - as regards heat transfer by conduction and radiation, no molecules move from hotter object A to cooler object B. How can heat move from A to B, if heat is molecules in motion, and no molecules move from A to B ?

The law of identity allows that a thing could continue to be the same thing, despite undergoing change. — Metaphysician Undercover

How can that be ?

In logic, the law of identity states that each thing is identical with itself. Gottfried Wilhelm Leibniz expressed it as "Everything is what it is". Wilhelm Wundt credits Gottfried Leibniz with the symbolic formulation, "A is A".

Object A, from the law of identity, is identical with itself.

I am taking object A as something that exists in the world, not as the name "object A". Object A and "object A" are different things. Object A exists in the world and "object A" exists in the mind. "Object A" is the name for object A.

All the properties object A has are necessary for object A to be object A, and all the properties object A has are essential for object A to be object A.

If object A changes into Object B over time, even if it has lost only one molecule, then object B cannot be the same as object A.

If the lectern before us were made of plastic instead of wood, it would be a different lectern to the wooden one that is actually before us. — Banno

Being made of wood is not essential of being a lectern.............By the law of identity all properties of a particular individual are essential properties.......... So we cannot say that it is necessarily made of wood, that might be a mistaken judgement. — Metaphysician Undercover

The law of identity
There is something in front of me. It has many properties: being made of wood, brown in colour, being in a lecture room, being 1.5m in height, not made of ice, etc. It must be true as @Metaphysician says: "By the law of identity all properties of a particular individual are essential properties". In the sense that all the properties this thing has are essential to making this thing, in that if this thing had different properties it would be a different thing. If this thing lost even one molecule, it would be a different thing. It must be true as @Banno wrote: "If the lectern before us were made of plastic instead of wood, it would be a different lectern to the wooden one that is actually before us."

We judge some properties of an object more essential than others
However, this would be inconvenient for humans in navigating their world if everything they saw in the world was continually changing. Therefore, for convenience, humans judge certain properties more essential than others. For example, one person could judge that being made of wood was more essential to being a lectern, and another person could judge that being in a lecture room was more essential to being a lectern. There is no correct judgement, it is a matter of personal judgement. It must be true as @Metaphysician wrote: "Being made of wood is not essential of being a lectern."

Kripke and Rigid Desgnators
Kripke wrote: i) "What do I mean by ‘rigid designator’? I mean a term that designates the same object in all possible worlds.", ii) "We can talk about this very object, and whether it could have had certain properties which it does not in fact have. For example, it could have been in another room from the room it in fact is in, even at this very time, but it could not have been made from the very beginning from water frozen into ice."

In order to make sense of objects in the world, those properties judged more essential than others required to maintain the identity of an object, are called by Kripke "rigid designators". Rigid designators are defined by personal judgement. For example, let a rigid designator of a lectern be "being made of wood", though it could equally well have been "being in a lecture room". As we have judged being made of wood is an essential property of a lectern, by definition, being made of wood becomes a property of a lectern.

It follows that as "being made of wood" is now part of the definition of a lectern. If I see an object that is not made of wood, then by definition it is not a lectern. It must be true as @Metaphysician wrote: "So we cannot say that it is necessarily made of wood, that might be a mistaken judgement". Because this definition of lectern doesn't include being in a lecture room, as a lectern may or may not be in a lecture room, the lectern is not necessarily in a lecture room.

Definitions are necessarily true a priori
Kripke wrote: i) "So we have to say that though we cannot know a priori whether this table was made of ice or not, given that it is not made of ice, it is necessarily not made of ice. " ii) "For example, being made of wood, and not of ice, might be an essential property of this lectern."

But what is a "lectern". What does "lectern" mean. The meaning of words cannot come empirically from observation of the world, in that, if I look at the world and see on the one hand a group of charging elephants and on the other hand a stand made of wood in a lecture room, it would be impossible to know a posteriori which of these "lectern" refers to. The meaning of "lectern" can only be determined a priori either from a dictionary or similar or from use within language. Therefore, the meaning of "lectern" is a priori and necessary.

Therefore, in Kripke's statement "being made of wood..........might be an essential property of this lectern.", "this lectern" may be replaced by "this something that is known a priori as being made of wood". This gives the statement "being made of wood..........might be an essential property of this something that is known a priori as being made of wood", which is an analytic statement, and from the law of identity, being made of wood is necessarily being made of wood.

Conclusion
Therefore, as a lectern has been defined as being made of wood, if this lectern is made of wood, then this lectern is necessarily made of wood. Such identity statements are therefore necessary and a priori.

Trouble is, we talked of heat well before we described it as the motion of molecules — Banno

Often, the cause of an effect is given the same name as the effect

Yes, I can experience a sensation in my mind such as pain. My pain as an effect in the mind may have a cause in the world. I see a thistle, and believe that the thistle is the cause of my pain. I need to know nothing about the nature of thistles in order to believe that the thistle was the cause of my pain. In Kant's terms, the thistle is a thing-in-itself.

Often, the cause of an effect is given the same name as the effect. For example, the sensation of red when looking at a red postbox. The sensation of sweet when having a sweet after dinner. The sensation of heat from a hot radiator. The sensation of a burning smell from a burning bonfire. The sensation of a bitter taste from an Angostura Bitter.

The fact that the name of an effect is the same as the name of its cause does not mean that the effect and its cause are the same thing.

whether or not the table is made of ice is always a human judgement. — Metaphysician Undercover

Yes, human judgement must come into it.

Suppose this lectern is made of wood and is in the lecture theatre

Kripke has made the judgement that being made of wood might be an essential property of this lectern, and being in a different room is a non-essential property. Someone else could have made the opposite judgement, that being made of wood is a non-essential property whilst which room this lectern is in is an essential property.

But keeping with Kripke's judgement that being made of wood might be essential property of this lectern..

Someone could say that there is a possible world where this lectern could have been made of plastic, which is highly likely. However, there can be many definitions of "possible worlds", but this is not what Kripke's means by "possible world". For Kripke, a "possible world" is a world in which this lectern keeps its essential properties.

Keeping with Kripke's understanding of "possible world" as a world where this lectern keeps its essential properties.

Therefore, this lectern, which is made of wood, has the essential property of being made of wood, meaning that in all possible worlds it is still made of wood. This lectern is necessarily made of wood in all possible worlds, because by definition, if this lectern is made of wood in the actual world it must also be made of wood in all possible worlds.

So, the statement "this lectern, which is made of wood in this actual world, must necessarily be made of wood in all possible worlds" is contingent first on Kripke's judgement that being made of wood might be an essential property of this lectern and second on Kripke's understanding of a possible world as one in which this lectern keeps its essential properties.

Sure. But not sure what your point is here. I don't see how this is a problem specific to Kripke's account, if that is what you are thinking. — Banno

How do we determine that two rigid designators refer to the same thing.

Kripke wrote: "To state the view succinctly: we use both the terms ‘heat’ and ‘the motion of molecules’ as rigid designators for a certain external phenomenon. Since heat is in fact the motion of molecules, and the designators are rigid, by the argument I have given here, it is going to be necessary that heat is the motion of molecules."

Therefore, as Kripke is saying that heat is a rigid designator, the motion of molecules is a rigid designator, and since "since heat is in fact the motion of molecules", the two rigid designators must be referring to the same thing.

As you wrote: "He provokes the difficult argument that it is necessary that heat is molecular kinetic energy, but contingent that we happen to feel this as the sensation we call heat."

When Kripke refers to "heat", is he referring to what is in the world as molecular kinetic energy, or is he referring to what is in the mind as the sensation of heat ?

As regards heat as the sensation of heat, Kripke writes:
1) "Martians, who do indeed get the very sensation that we call “the sensation of heat”"
2) "Then these creatures could be such that they were insensitive to heat; they did not feel it in the way we do; but on the other hand, they felt cold in much the same way that we feel heat."

As regards heat is the motion of molecules, Kripke writes
1) "First, imagine it inhabited by no creatures at all: then there is no one to feel any sensations of heat. But we would not say that under such circumstances it would necessarily be the case that heat did not exist; we would say that heat might have existed, for example, if there were fires that heated up the air."

If "heat" refers to the sensation of heat in the mind, then how can there be identity between something that exists in the mind and something that exists in the world, the motion of molecules.

If "heat" refers to the motion of molecules, there are two possibilities: i) heat is no more than the motion of molecules, heat is a synonym for the motion of molecules, and therefore "heat is the motion of molecules" is an analytic statement and known a priori, ii) heat exists over and above the motion of molecules, heat exists independently of the motion of molecules, and therefore heat would exist even if there were no molecules in motion, in which case heat could only be discovered a posteriori. As current scientific theory does not propose that heat exists independently of the motion of molecules, heat must be a synonym for the motion of molecules, a case of self-identity. As Kripke said "What properties, aside from trivial ones like self-identity"

Therefore, the statement "heat is the motion of molecules" is either an analytic statement known a priori or requires an understanding as to how there can be an identity between something in the mind and something in the world.

No it isn't. The heat moves from one body to the other, in a process that can be described with mathematical predictability. Nothing metaphorical about it. — Banno

Kripke said “Heat is the motion of molecules”, which is incorrect.

Heat is the energy transferred between objects due to a temperature difference between them. As you said, the amount of heat gained or lost by a sample (q) can be calculated using the equation q = mcΔT, where m is the mass of the sample, c is the specific heat, and ΔT is the temperature change. Heat is a measurement, it doesn't have an independent existence. An object does not possess heat, an object possesses internal energy.

If object A travelling at 5m/s hits a stationary object B, the speed of object A reduces to zero, and the speed of B increases to 5m/s. Something called "speed" has not literally moved from A to B. Speed is a measurement, not something that has an independent existence


If object A at 30deg C touches object B at 20deg C, the temperature of object A will reduce and the temperature of object B will increase. Something called "heat" has not literally moved from A to B. Heat is a measurement, not something that has an independent existence

The statement "The heat moves from one body to the other" is not incorrect as a figure of speech.

I wouldn't read it that way. Rather, Kripke has already made his case and is applying his account to heat. I think we can drop the heat argument without much impact on Kripke's approach to modality. He is not trying to justify his account of possible world semantics by appeal to heat. — Banno

Yes, Kripke first makes his case that if an identity statement is true, then the identity statement is necessary, and only later introduces the examples of names, heat and my pain.

But isn't his argument circular, in that if the identity statement "the Moon is made of blue cheese " is true, then he is arguing that the moon is necessarily made of blue cheese. Similarly, if the identity statement "the Moon is not made of blue cheese" is true, then the Moon is necessarily not made of blue cheese.

Kripke wrote " Identity statements..........That is to say, they are necessary if true; of course, false identity statements are not necessary." (abstract)

The problem remains in how do we determine whether an identity statement is true or not. How do we determine that two rigid designators refer to the same thing.

Kripke's case is that true identity statements are necessary
Kripke wrote: "To state finally what I think, as opposed to what seems to be the case, or what others think, I think that in both cases, the case of names and the case of the theoretical identifications, the identity statements are necessary and not contingent". (page 171)

Kripke makes a general argument
"If names are rigid designators, then there can be no question about identities being necessary, because ‘a’ and ‘b’ will be rigid designators of a certain man or thing x. Then even in every possible world, a and will both refer to this same object x, and to no other, and so there will be no situation in which a might not have been b. That would have, to be a situation in which the object which we are also now calling ‘x’ would not have been identical with itself". (page 181)

Kripke gives an example using "this lectern"
"Here is a lectern......What are its essential properties............being made of wood, and not of ice, might be an essential property of this lectern...............could this very lectern have been made from the very beginning of its existence from ice.............If one had done so, one would have made, of course, a different object. It would not have been this very lectern........The conclusion ☐P is that it is necessary that the table not be made of ice, and this conclusion is known a posteriori, since one of the premises on which it is based is a posteriori" (page 180)

Later on, Kripke refers to names, heat and my pain.
1) "If names are rigid designators, then there can be no question about identities being necessary" (page 180)
2) "We use both the terms ‘heat’ and ‘the motion of molecules’ as rigid designators for a certain external phenomenon". (page 187)
3) "In fact, it would seem that both the terms, ‘my pain’ and ‘my being in such and such a brain state’ are, first of all, both rigid designators". (page 188)

It may well be that true identity statements are necessary. The problem remains in knowing whether the identity statement is true or not. How do we know in the first place that "Cicero is Tully", "heat is the motion of molecules" and "my pain is my being in such and such a brain state" ?

Don't you think it's the word "heat" which is the most metaphorical here...Yet it maintains descriptive power by way of metaphor, so it is still used. — Metaphysician Undercover

Yes, it is a concept that exists in the mind and not the world, such as pleasure, pain, government, democracy. But as a concept, it does have great descriptive power, even if what it is describing doesn't literally exist in the world.

"Heat" is really meaningless then, because if it referred to the activity of heating or cooling, it would necessarily be in the body, in order that the body could heat up or cool down. Or is "heat" just metaphor to you? — Metaphysician Undercover

If heat is not energy, this throws a spanner in the works in Kripke's argument for a posteriori necessity.

"Heat" has meaning as a measurement.

Heat is a measurement of the change in energy of a body. Heat is not a substance. A thermodynamic system does not contain heat.

Consider two bodies, one 1,000 kJ hotter than the other. Consider two bodies, one 80 metres taller than the other.

In what sense do measurements exist. In what sense does "1,000 kJ hotter" exist. In what sense does "80 metres taller" exist.

If The Empire States Building is 80m taller than The Eiffel Tower, where does "being 80m taller" exist. Does it exist in the world independently of any object, or does it exist in the mind of an observer.

If body A is 1,000 kJ hotter than body B, where does "being 1,000kJ hotter" exist. Does it exist in the world independently of any object, or does it exist in the mind of an observer.

It can only exist in the mind of the observer as a second-order concept, as Frege and Russell argued.

If heat is the measurement "being 1,000 kJ hotter", where does "being 1,000 kJ hotter" exist. Where does heat exist?

If heat is the transfer of thermal energy, and we're using the term "heat" consistently, then in each and every instance where we use "heat", we ought be able to substitute that term with "the transfer of thermal energy", and retain all sensibility. — creativesoul

Could I be thrown off a philosophy forum for talking about the scientific nature of heat
In order to avoid being thrown off the thread for talking about the nature of heat, my reason is as follows:

Kripke concludes: "To state finally what I think, as opposed to what seems to be the case, or what others think, I think that in both cases, the case of names and the case of the theoretical identifications, the identity statements are necessary and not contingent."

One of the main planks of Kripke's justification is that “Heat is the motion of molecules will be necessary, not contingent, and one only has the illusion of contingency"

Thermal energy is due to the motion of molecules. Therefore, one of Kripke's main justifications for a posteriori necessity is his belief that heat is thermal energy.

If heat is, in fact, not thermal energy, one of Kripke's main planks disappears. This casts doubt on the other planks in his argument, which in turn casts doubt on his conclusion regarding a posteriori necessity.

The word "transfer" is being used as a metaphor
The statement "The amount of heat gained or lost by a sample (q) can be calculated using the equation q = mcΔT, where m is the mass of the sample, c is the specific heat, and ΔT is the temperature change" is being used metaphorically rather than literally. Heat is a measure of the change in energy of a body. As a thermodynamic system does not contain heat, a body cannot gain or lose heat.

Britannica writes: "heat, energy that is transferred from one body to another as the result of a difference in temperature" Again, the word "transfer" is a metaphor. Heat has not literally been transferred from one body to the other.

Language is fundamentally metaphoric
Language, both in daily and scientific use is fundamentally metaphoric. Language as we know it couldn't exist without metaphor.

When you say "The above looks suspiciously like an equivocation fallacy", "A substitution exercise shows it nicely", "If heat is the transfer of thermal energy", "perform this exercise", and "something is off" you are using language metaphorically.

George Lakoff and Mark Johnson in Metaphors We Live By argue that metaphors are not merely stylistic, but are pervasive in everyday life, not just in language, but also in thought and action.

Andrew May in his article Metaphors in Science writes: "What is a scientific theory if not a grand metaphor for the real world it aims to describe? Theories are generally formulated in mathematical terms, and it is difficult to see how it could be argued that, for example, F = ma "is" the motion of an object in any literal sense. Scientific metaphors possess uniquely powerful descriptive and predictive potential, but they are metaphors nonetheless."

The word "transfer" is being used as a metaphor. Language would not exist as we know it without the use of metaphor. The use of metaphors is unavoidable in language, and we have to depend on context to tell us whether a word is being used metaphorically or not.