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, — RussellA

Trouble is, we talked of heat well before we described it as the motion of molecules. And not just the sensation, but what was needed to kindle a fire and boil the kettle and make winter bearable. Not just the sensation.

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.

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

Being made of wood is not essential of being a lectern. However, if we are talking about a particular thing, that lectern in particular, then every property is essential to it being the very thing which it is. That is the law of identity. So when we talk about particulars, every property is essential, and there is no need to make the arbitrary judgement of which properties are essential.

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. — RussellA

This is where things get difficult for Kripke. By the law of identity all properties of a particular individual are essential properties. So if he wants to bring a particular into a possible world (where a particular could have properties other than it does), he violates the law of identity. This is why the standard, traditional procedure, is to represent the particular object as a logical subject. Then we maintain the separation between the logical subject, which may partake of may possibilities, and the material object which by the law of identity is what it is, necessarily, and therefore allows of no other possibilities

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. — RussellA

The problem I see here is the judgement factor. That particular lectern is judged to be made of wood. That is a human judgement which could conceivably be wrong. So we cannot say that it is necessarily made of wood, that might be a mistaken judgement. However, we can represent that particular object as a subject, named "a wooden lectern". This subject is necessarily made of wood, because it is stipulated. Then we can place that subject, a wooden lectern", in whatever possible world we like, where it is always necessarily made of wood. The point here being that we make a distinction between the material object which is always exactly what it is (by the law of identity), and what we say of that object. The possible worlds consist of what we say. This allows for the reality that we may be mistaken in our judgement of what is a property of any particular object.

However, if we are talking about a particular thing, that lectern in particular, then every property is essential to it being the very thing which it is. That is the law of identity. — Metaphysician Undercover

Again, this odd interpretation has the result that when one says the lectern might have been in the other room, one is talking about a different lectern.

By the law of identity all properties of a particular individual are essential properties. — Metaphysician Undercover

this is were Meta goes amiss.

Again, this odd interpretation has the result that when one says the lectern might have been in the other room, one is talking about a different lectern. — Banno

No, you would be talking erroneously about the lectern in question. It's not the case that it might have been in a room other than the one it is in, unless you mean that it might have been earlier or might be later in another room.

...erroneously... — Janus

As if "The lectern might have been in the other room" were false.

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.

Again, this odd interpretation has the result that when one says the lectern might have been in the other room, one is talking about a different lectern. — Banno

That's right, as it should be, as Janus indicates. That's because if the lectern we are talking about is in the other room, it is a different lectern from the one we know to be in this room, necessarily. "Necessarily" here is supported by the law of identity which is the premise which forces this conclusion.. Just like, if the lectern we're talking about is made of plastic, when this one we know to be made of wood, we would necessarily be talking about a different lectern.

That's how the law of identity works to prevent sophistry. It's very intuitive, and restrict us to saying things we truly believe, while sophistry is a matter of saying deceptive things. You don't truly believe that the lectern which is in this room might be in the other room, do you?

Yes, "might have been" implies a different time, and so we can allow that the lectern might have been in a different room, at a different time, but to use "might have been" to imply at the same time, is just deceptive speaking.

As if "The lectern might have been in the other room" were false. — Banno

Yes, it's false because it is deceptive speaking. It's deceptive speaking because it employs ambiguity, as "might have been" implies a different time, whereby the described possibility would be acceptable, but it is used to mean at the same time, whereby the described possibility is unacceptable (by the law of identity).

That's why I asked, do you really believe that the lectern which is in this room might be in the other room. If not, then what are you saying with "might have been"?

Again, this odd interpretation has the result that when one says the lectern might have been in the other room, one is talking about a different lectern. — Banno

Actually, it’s a demonstration of the different “categories of truth”, and how it is his “wish to distinguish them”, beginning at the bottom of pg176. It isn’t about different lecterns; it’s about different ways of knowing about one lectern.

He says, “We can certainly talk about this very lectern and whether it can have certain properties which in fact it does not have. For example, it could have been in another room from the one it was in fact in, even at this very time, but it could not have been made from the very beginning from water frozen into ice”.

Here he’s saying this lectern cannot have any material property other than the essential one it does, but we can still talk about it as if space were one of its properties. Which is what we do when we say this lectern could have been in another room, but it couldn’t be made of ice.

One of the properties “which in fact it does not have”, regarding the lectern in particular and objects in general, is, of course, space. And, as hinted, so too is time a property objects in general cannot have.

Thus is the conflict incurred between Kripke’s “categories of truth” and Russell’s so-called “scope of description”, re: this/that modal distinctions, whereby a necessary identity statement regarding THIS thing, that THIS thing cannot be in THAT place on the one hand, in juxtaposition to the contradictory attribution of space and time as properties, on the other.

Logical statements are validated by themselves, but their proofs are in experience alone. It is far easier to prove THIS thing can be in THAT place and remain THIS thing, then to prove THIS thing in THAT place is not THIS thing.

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.

However, this would be inconvenient for humans in navigating their world if everything they saw in the world was continually changing. — RussellA

This is the difficulty. The law of identity allows that a thing could continue to be the same thing, despite undergoing change. That is the temporal extension of a thing. So the status of "thing" simply implies some form of temporal continuity. From this perspective we understand "change" as relative to the supposed temporal continuity (Newton's first law for example). But this assumed temporal continuity is inductive in nature, and it cannot actually be proven due to the reality of change which is happening everywhere, to everything, all the time. Therefore the law of identity, along with the prerequisite assumption of "things" (a "thing" being a temporal continuity of sameness) presupposes without justification the necessary existence of things, and the necessity of temporal continuity of sameness. Because of this, it is fundamentally defective.

This is why Hegel attacked the law of identity, giving logical priority to "becoming", making being and not being, and therefore the existence of actual things, simply a human judgement which we impose on the world of becoming. The idea that the existence of external objects is intuited rather than saying that the external object has real independent existence, I believe is basic to phenomenology.

I don't see what relevance this has to the topic, unless you are claiming that the motion of molecules causes heat. But that's not right, although it might be said to cause the sensation of heat.

That's because if the lectern we are talking about is in the other room, it is a different lectern from the one we know to be in this room, necessarily. — Metaphysician Undercover

That's risible.

And you continue to mix the law of identity with the identity of Indiscernibles.

But it's on par with many of you other arguments. I'll leave you to it.

It must be true as Metaphysician says: "By the law of identity all properties of a particular individual are essential properties". — RussellA

Then you are now claiming that there are no properties that are not essential, and hence that differentiating essential form nonessential properties is an error.

The consequence is that any change in the properties of an individual result in a different individual.

I don't think that is going to work out well.

I'll invite you to reconsider the difference between the law of identity, A=A, and the identity of indiscernibles, that if everything true of x is true of y, x is identical with y. These are different laws.

I'll maintain that @Metaphysician Undercover is mistaken and that an object's properties may be subject to change and that it makes sense to talk of essential an non-essential attributes.

As if "The lectern might have been in the other room" were false. — Banno

It is false; it is a mere logical possibility, nothing more than a matter of mere words.

Here he’s saying this lectern cannot have any material property other than the essential one it does — Mww

I don't agree. He happened to use a spatial example - the lectern might have been in another room. But he might equally have used a material example such as that the lectern might have been painted pink or had his name engraved on it. These are ways in which the properties of that very lectern may have been otherwise.

But to suppose that the lectern before us may have been made of ice is to suppose that the lectern before us were a different lectern.

Kripke is not claiming that the lectern could not have any material properties other than it does have.

It is false; it is a mere logical possibility, nothing more than a matter of mere words. — Janus

"The lectern might have been in the other room"

Make up your mind - is it false or is it logically possible?

I say it is a true proposition about this lectern. This very lectern might have been in the other room.

It is logically possible but not actually possible. What is merely logical possible tells us nothing beyond what we are capable of coherently and consistently imagining, because it is really just playing with words.

It is logically possible but not actually possible. — Janus

A nonsense expression. Perhaps you mean it is logically possible but not actual. Sure. It remains that "The lectern may have been in the other room" is a meaningful sentence. And it seems to be true. It is also true that the lectern is not actually in the other room. There is no contradiction between these sentences:

The lectern is in this room and the lectern might have been in the other room.

A nonsense expression. — Banno

No, a valid distinction which you can't see apparently. Try looking beyond words, you might actually arrive at some new thoughts.

Try looking beyond words — Janus

SO it's a distinction that you cannot express. :brow:

Then it's a distinction that makes no difference.

No it's easy to express. Logically the lectern could have been in a different room, but for all we know actually it could not have been, since to change one thing is to change everything. In any case it's something that could never be tested, and we certainly don't know that it is actually possible, just because we can consistently say that it is possible.

Logically the lectern could have been in a different room, but for all we know actually it could not have been — Janus

A nonsense, again. Actually, it is in this room; Possibly, it might have been in the other. That's it.

What you want to claim might be that there are consequences, including those that are both unforeseen and unforeseeable, for things being other than they are. Sure. Sorting out those consequences begins with a consistent semantics, as provided by Kripke.

Hence it remains true that

The lectern is in this room and the lectern might have been in the other room.

A nonsense, again. Actually, it is in this room; Possibly, it might have been in the other. That's it. — Banno

Have it your way: I see no point in arguing further against dogma, so I'll leave you to it.

Here he’s saying this lectern cannot have any material property other than the essential one it does
— Mww

I don't agree. (…) he might equally have used a material example such as that the lectern might have been painted pink or had his name engraved on it. — Banno

Of course, but these are not properties the lectern cannot have. They do not represent the properties the lectern must have such that to not have them the lectern wouldn’t be “this very object”. You’re talking about what it can have; he’s talking about what it cannot have. If space is a property it cannot have, THIS lectern cannot be in THAT room, for then it would be in two spaces simultaneously.

These are ways in which the properties of that very lectern may have been otherwise. — Banno

These are ways that very lectern’s properties are cumulative without contradiction. Add all the properties you like, but it’s still going to be made of wood, it’s still going to be in this room. As long as the subject making the statements is as well, which is tacitly understood to be the case.

If you keep working at it, you might begin to understand how possible world semantics deals with your misgivings. The actual world is one of many possible worlds, which provide a consistent framework in which to parse modal sentences. The actual world cannot be other than it actually is, which is what you seem to be insisting. That's part and parcel of the possible world interpretation.

THIS lectern cannot be in THAT room, for then it would be in two spaces simultaneously. — Mww

Of course the lectern might be in the other room, in which case it would not be in this room. Supposing that the lectern might have been in the other room is different to supposing that it might have been in both this room and in the other room.

Add all the properties you like, but it’s still going to be made of wood, it’s still going to be in this room. — Mww

Sure, it's actually in this room. But it might possibly have been in the other. But if the lectern in this room were made of ice, it would be a different lectern. Being not made of ice is an essential property, being in this room, being pink and having "Kripke was here" engraved on it, inessential.

And you continue to mix the law of identity with the identity of Indiscernibles. — Banno

You continue to demonstrate that you have no idea what the law of identity actually states. You state your rendition as "A=A", but you continue to show that you have no idea what this represents.

I'll maintain that Metaphysician Undercover is mistaken and that an object's properties may be subject to change and that it makes sense to talk of essential an non-essential attributes. — Banno

Not only do you have no idea what the law of identity states, you totally misrepresent what I say. Look at the following, what I said, and please retract what you said about me above.

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

Regardless of whether a thing changes or not, a thing is necessarily the thing which it is, by the law of identity. And, at any given point in time, all of its attributes are necessary to it being the thing that it is. Therefore all of its attributes are necessary. That is implied by the law of identity (a thing is the same as itself). If it does not actually have all the attributes which it has, it is not the same as itself. Therefore all of a thing's attributes are necessary, by the law of identity.

I don't disagree with any of that, but I see nothing in possible world semantics that is anything more than determining what can obviously be imagined without logical contradiction.
So I don't see anything to be gained by pursuing it further, since it is all pretty obvious until it becomes murky and there seems to be no way to definitively dispel the inevitable murkiness.

I'll maintain that Metaphysician Undercover is mistaken and that an object's properties may be subject to change and that it makes sense to talk of essential an non-essential attributes. — Banno

And this! I'm surprised to see you advocating essentialism.

but I see nothing in possible world semantics that is anything more than determining what can obviously be imagined without logical contradiction. — Janus

That's what it is - a tool for working through those apparent contradictions.

...until it becomes murky... — Janus

Just so, as here.

...essentialism — Janus

Hardly. There are issues here, but if we cannot agree on the framework within which they are to be discussed, the topic cannot progress.