As per the OP section "Argument in defence of the PSR", logic (and the PSR) are first principles of metaphysics. This means they exist in all possibe worlds, which means they have necessary existence. Thus, logic and the PSR exist necessarily or inherently. This is an internal reason which is valid under the PSR. — A Christian Philosophy

There are many different type of logic, suggesting that no one logic exists necessarily. For example, there is Propositional Logic, First Order Logic, Second order logic , Higher order logic, Fuzzy logic, Modal logic, Intuitionistic Logic, Dialetheism, etc.

Logical systems also change, also suggesting that no one logical system is necessary. For example, today few would maintain that Aristotle's logic doesn't have serious limitations.

The Law of Identity "A is A" is one of the three Laws of Thought.

The Laws of Thought are axiomatic rules, taken to be true to serve as a premise or starting point for further reasoning and argument. In other words, taken to be true but not necessarily true.

The Law of Identity was described as fundamental by Aristotle, as primitive by Leibniz and to a certain extent arbitrary by George Boole.

"A is A" exists as a convenient axiom, not as a necessity.

The PSR states that everything has a sufficient reason. It is true that we use the Law of Identity "A is A" for a reason, but this is an external reason, in that it is convenient for further reasoning and argument. This is not a "sufficient reason" in terms of the PSR

We use the Law of Identity as an axiom as a convenience not because it has any internal necessity.

The Law of Identity, as an example of logic, is used for the external reason that it is convenient in further reasoning, not from any reason of internal necessity.

Yes, they have the freedom to do this. I don't believe that, do you? — Metaphysician Undercover

I think it is more likely that Free Will is an illusion than an actual thing.
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My usage was the latter sense of "laws of nature". — Metaphysician Undercover

In modern days we understand this as inductive reasoning, cause and effect, and laws of physics. This inclines us to think that these formulae are abstractions, the product of human minds, existing as ideas in human minds. And this is correct, but this way of thinking detracts from the need to consider some sort of "form" which preexists such events, and determines their nature. — Metaphysician Undercover

A "law of nature" in this sense necessarily precedes the event, because the laws of nature are what makes things act the way that they do. — Metaphysician Undercover

Laws of Nature
IE, you were referring to the Laws of Nature as "principles which govern the natural phenomena of the world" rather than "descriptions of the way the world is".

The question is, is it strictly true that "descriptions of the way the world is" are posterior to events and "principles which govern the natural phenomena of the world" are prior to events?

There is an overlap in Laws of Physics and Laws of Nature. For example, Newton's three laws of motion are described by the SEP article Laws of Nature as Laws of Nature and are described by the web site www.examples com as Laws of Physics.

By observing many times that the sun rises in the east, by inductive reasoning, I can propose the law that "the sun rises in the east". It is true that this law is posterior to my observations. But it is equally true that this law is prior to my observing the next sun rise.

When does a law become a Law of Nature?

If for hundreds of years hundreds of scientist have observed that F=ma, then this is sufficient for F=ma to become a Law of Nature.

But in principle the Law of Nature that F=ma is no different to my law that "the sun rises in the east", apart from the number of observations.

This Law of Nature is posterior to observations and prior to the next observation in exactly the same way that my law was posterior to my observations and prior to my next observation.

Whilst it is true that Laws of Nature are prior to the next event, they are also posterior to previous events.

The Law of Nature that F=ma is not the cause of the next event, it does not make the next event act as it does act and it does not determine the next event, but is a prediction about what the next event will be based on past experience.

Aristotle
Whereas for Plato Form is prior to physical things, for Aristotle's hylomorphic scheme, Form and Matter are intertwined. It may well be that Form is Matter, united by the Formal Cause.

As Form cannot exist independently of Matter, Form cannot exist prior to Matter but must be contemporaneous with it.

Free will allows a new, undetermined event to enter into the chain of causation determined by the past, at any moment in time. — Metaphysician Undercover

Some argue that Free Will is an illusion.

Since the prior forms are "idea-like" as immaterial, and the cause of things being the way that they are, in much the same way that human ideas cause artificial things to be the way that they are, through freely willed activities, we posit a divine mind, "God". — Metaphysician Undercover

The material and the immaterial

I can understand a God as being a prior cause to physical events, providing one accepts the possibility of a God.

I agree that human concepts can cause changes in the physical world, in that having the concept of thirst can cause a bottle of water in the world to move

The existence of Free Will is debated. Some argue that it is an illusion.

However, I don't agree that concepts in the mind and the Laws of Nature in a world outside the mind are immaterial, but rather that they are fully material.

As regards the particular Law of Nature that when there are regions of excess positive and negative charge within a cloud lightning occurs, there is nothing immaterial about this. The event is fully explainable as the deterministic behaviour of matter and forces between matter.

As regards concepts in the mind, as software exists within the hardware of a computer, concepts exist in the physical structure of the brain. If change the physical structure of the brain, then change the concepts within that physical structure.

No evidence has ever been presented of the dissociation of concepts from the brain, in that if a living brain moved from the living room to the dining room, no one would suggest the possibility of the concepts remaining in the living room.

IE, some may believe in God and Free Will, but it seems to me that they are not necessary as explanations of the relationship between mind and world outside the mind.

A common way of representing the difference between the two types of "form" are as the laws of physics (human abstractions), and the laws of nature (what the laws of physics are supposed to represent, which causes things to behave the way that they do). Aristotle provided much guidance for separating the two senses of "form", the causal as prior to events, and the human abstractions as posterior to events. — Metaphysician Undercover

There is a lot in your post, but taking your points one by one.

I observe a hundred times that when there are regions of excess positive and negative charge within a cloud then lightning occurs. I can ask why.

I can conclude that there is a Law of Nature such that when there are regions of excess positive and negative charge within a cloud lightning occurs.

There are two aspects to a "Law of Nature": as it exists in the mind and as it exists in a world outside the mind.

As regards the Law of Nature as it exists in a world outside the mind

Am I right is thinking that an Aristotelian Form and Law of Nature are analogous?

My question is, is it in fact the case that a Law of Nature precedes the event it describes, or is the Law of Nature contemporaneous with the event it describes. My belief is the latter.

If the Law of Nature is contemporaneous with the event it describes, and if the Aristotelian Form may be thought of as a Law of Nature, then the Aristotelian Form will also be contemporaneous with the event it describes.

Suppose there is a cloud with regions of excess positive and negative charge. This is not a prediction of a future lightning strike, but immediately gives rise to a lightning strike. The Law of Nature determines what does happen not what will happen.

It therefore seems that an Aristotelian Form, as with a Law of Nature, rather than pre-existing an event, can only be contemporaneous with an event.

IE, the Laws of Nature as abstractions in the mind are a posteriori to events, but the Laws of Nature in a world outside the mind, and by analogy the Aristotelian Forms, must be contemporaneous with events.

Plato thought that since things exist as types, then the form, or type, idea, must be prior to the thing itself, to cause it to be the type of thing that it is — Metaphysician Undercover

There is a particular lightning strike, and being a particualr instance is a token. Several lightning strikes would create a class of events, The Lightning Strike, which would be a type.

In practice, can anyone give any explanation, other than in the mind of God, where a Lightning Strike could exist prior to a lightning strike?
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Aristotle showed that since a particular thing has a form unique to itself, which must be prior in time to the thing itself to account for it being the thing that it is and not something else, forms must be prior to material things. — Metaphysician Undercover

A particular lightning strike has a particular form, which is unique to itself, and is different to the form of tree.

Suppose the form of the lightning strike existed 1,000 years before the actual lightning strike happened. Then by the same logic, to account for the form of the lightning strike being the thing that it is rather than something else, the form of the lightning strike must have existed prior to 1,000 years before the actual lightning strike, ad infinitum until the beginning of existence.

Therefore, the form of the lightning strike must have existed at the beginning of existence. Similarly the form of every event must have existed at the beginning of existence.

In other words, according to Aristotle, the form of this post, which has a form unique to itself, must have been determined at the beginning of existence, 13.7 billion years ago, which is a scary thought.
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This indicates that there must be something similar to ideas, forms, which are prior in time to material existence, therefore outside of human minds. — Metaphysician Undercover

Expanding to minds rather than just human minds, as as I am sure that the dinosaur had a mind.

I have the idea that lightening strikes are terrifying.

In practice, prior to minds, what was terrified by the idea of a lightning strike?
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Isn't "force" just a concept? — Metaphysician Undercover

Yes. That's the problem.

But every word in language refers to a concept, in that "fundamental" is a concept, "particle" is a concept, "and" is a concept, etc.

It can also be argued that every word in language should be taken as a figure of speech rather than literally. For example, George Lakoff and Mark Johnson wrote the book Metaphors We Live By 1980. In science, Andrew May in Science 2000 argued that even Newton's second law, F = ma is a metaphor.

But concepts don't exist outside the mind.

Therefore, the problem is that language is using concepts which only exist in the mind to describe a world that exists outside the mind, where such concepts don't exist.

I agree that I am using the concept of "force", which exists in my mind, to describe something in the world, even though the concept "force" doesn't exist in the world.

And this is true for every word in language.

Language as a whole is using concepts, including the colour red and number, to describe a world where those concepts don't exist.

One possible conclusion would be that the world we observe exists in the mind, not outside the mind, in a Kantian kind of way.

How could a wavelength of 700nm exist in the world? — Metaphysician Undercover

You are right. How can I say on the one hand that "numbers exist in the mind but not the world" but on the other hand say that "science tells me that a wavelength of 700nm exists in the world", when a wavelength of 700nm depends on the existence of numbers.

All I can say is that in order to communicate my ideas I can only use language.

My premise is that ideas only exist in the mind. This would lead to the paradox that if I am able to successfully communicate my ideas using language, then it follows that, as language exists outside the mind, these ideas now exist outside the mind, thereby negating my original premise.

All I can conclude is, as ideas only exist in the mind, and language exists outside the mind, it is impossible to communicate my ideas using language.

This sounds a bit like 6.54 of Wittgenstein's TLP, where he wrote

My propositions serve as elucidations in the following way: anyone who understands me eventually recognizes them as nonsensical, when he has used them—as steps—to climb beyond them. (He must, so to speak, throw away the ladder after he has climbed up it.)

However, saying that, as an Existence Nihilist, I don't believe that wavelengths exist in the world. Hawthorne and Cortens (1995) spoke for the nihilist thus: “the concept of an object has no place in a perspicuous characterization of reality”.

I believe a world outside the mind exists, but not a world of objects, whether chairs or wavelengths, but rather a world of fundamental particles and forces existing in space and time.

As regards language, it can be argued that language, including the language of science, is more metaphorical rather than literal.

For example, metaphors are commonly used in science, such as: evolution by natural selection, F = ma, the wave theory of light, DNA is the code of life, the genome is the book of life, gravity, dendritic branches, Maxwell's Demon, Schrödinger’s cat, Einstein’s twins, greenhouse gas, the battle against cancer, faith in a hypothesis, the miracle of consciousness, the gift of understanding, the laws of physics, the language of mathematics, deserving an effective mathematics, etc

In this sense, I am using the expression "numbers exist in the mind but not the world" literally and the expression "science tells me that a wavelength of 700nm exists in the world" metaphorically.

Unfortunately, it is in the nature of language to mix literal and metaphorical expressions, and it is only the context that enables the reader to distinguish between the two.

Colors we project mentally are compatible to what exists in nature it seems, we know or assume others are projecting that color as well...animals, plants included living things adapting to environment and survival instincts have developed with time. — Kizzy

The OP is about the ontological status of ideas. It goes on to ask "So, chairs exists and numbers subsist? Is that a common understanding?"

I agree when you say:
1) "Colors we project mentally are compatible to what exists in nature it seems"
2) "Vision is an important sense that humans/animals have."

As regards:
3) "we know or assume others are projecting that color as well.......animals, plants included living things adapting to environment and survival instincts have developed with time."

I agree that it is more than likely that when I see a postbox emitting a wavelength of 700mn, my subjective experience of the colour red is the same as everyone else's, all things being considered equal. After all, life has evolved over 3 billion years in synergy with its environment. However, it is not something that I can ever know in the absence of telepathy.

When I observe a postbox, I know that the colour red exists in my mind, and science tells me that a wavelength of 700nm exists in the world.

When I observe the world, I see the colour red, meaning that either i) a wavelength of 700nm is the colour red in the absence of any observer, which I find hard to accept or ii) I project my subjective experience of the colour red onto the world, which I find easier to accept.

As with colour, similarly with number, such that numbers exist in my mind but not the world. When I observe the world and see numbers, I have projected my subjective experience of numbers onto the world.

As colour exists in the mind but not the world, numbers exist in the mind but not the world.

Regarding the word "exist, as unicorns exist in literature but not the world, colours and numbers exist in the mind but not the world.

The word "subsist" is unnecessary.

Logic has a reason for existing, as provided in the OP under section "Argument in defence of the PSR". — A Christian Philosophy

Is a logical necessity a sufficient reason or a Brute Fact.

I agree that:
1) The Unrestricted PSR states that everything has a sufficient reason
2) "Logic is part of the fabric of reality"
3) Logically A = A

However, what is the reason that A = A?
What is the reason for the existence of logic?
If logic has no reason, then logic is a Brute Fact.
Brute Facts are unexplainable and uncaused.
That logic is part of the fabric of reality is not sufficient reason why logic is part of the fabric of reality.
If, for example, A = A is a brute fact, then the Unrestricted PSR is no longer valid.

As regards your argument that "logic has a reason for existing"

I agree that
1) Truth means conformity with Reality
2) We discover Truth using Reason
3) Reason uses Deduction and Induction
4) An example of Deduction = i) the sun rises in the east, ii) therefore tomorrow the sun will rise in the east
5) An example of Induction = i) for the past 100 days the sun has risen in the east, ii) therefore the sun rises in the east.
6) If reason can find truth, then reason must mirror reality.

However, I don't agree that
1) "deduction is equivalent to the principle (or laws) of logic, in that deduction is based on an axiom (the sun rises in the east) that may or may not be true.
2) "induction is equivalent to the principle of sufficient reason", in that induction is assuming the regularity of nature, which may or may not be true, as pointed out by Hume.
3) "Reason finds truth", in that there is no logical necessity that either deduction or induction find the truth.

IE, we have no reason to think that logic has a reason for existing.

If logic has no reason for existing, then logic is a brute fact.

If logic is a brute fact, then the Unrestricted PSR is not valid.

Clearly sufficient reason and sufficient cause are there, whereas reason is more logic and cause is more physical. — jgill

An example of logic would be the Modus Ponens. i) IF P THEN Q ii) P iii) THEN Q

Let P and Q be physical facts, such that P = it rains and Q = I get wet

In Ordinary Language:
The reason I get wet is because it rains.
The cause of my getting wet is because it is raining.

Reason and cause can be purely logical:
The reason for Q is P providing that IF P THEN Q.
The cause of Q is P providing that IF P THEN Q.

Such logic may then be applied to physical facts.

Reason and cause are treated the same.

The fact that we are discussing something is not the evidence for existence of something. We can discuss about the unicorn or a flying pig. Does it mean the unicorn or flying pig exist? — Corvus

They exist in literature and in the mind as thoughts.

If either the unicorn or flying pig didn't exist somewhere, then you couldn't have written your post.
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"Numbers and colours exist somewhere"? Somewhere is like saying nowhere. — Corvus

The expression "exists somewhere" does not mean "exists nowhere".

Where about in the brain do you see numbers existing in physical form? — Corvus

P1 - Numbers and colours exist somewhere otherwise we couldn't be discussing them.
P2 - We know that numbers and colours exist in the mind because we are aware of them.
P3 - We observe the colour red even though colours don't exist in the world. What exists in the world is the wavelength 700nm. We mentally project the colour red onto the world that we are observing.

C1 - Similarly, it is possible that even though we observe numbers in the world, numbers need not exist in the world, as we can mentally project numbers onto the world.
C2 - As it is possible that numbers need not exist in the world, there need be no metaphysical angst about numbers existing in the world.

P4 - A calculator can manipulate numbers within the physical structure of the calculator in a deterministic and explainable way.

C3 - There needs be no metaphysical angst about numbers existing in a calculator.

P5 - Similarly, there is no reason why the brain cannot manipulate numbers within the physical structure of the brain in a deterministic and explainable way.

C4 - Similarly, there needs be no metaphysical angst about numbers existing in the mind.
C5 - Any metaphysical angst about numbers is unnecessary.

Logical necessity is a type of sufficient reason. It is reason type 1 in the OP section "PSR in Metaphysics". — A Christian Philosophy

If you accept an unrestricted form of the Principle of Sufficient Reason (PSR), you will require an explanation for any fact, or in other words, you will reject the possibility of any brute, or unexplainable, facts. (SEP - PSR)

Is logical necessity a brute fact?

For example, is the logical necessity that "A triangle has three sides" a brute fact?

A Brute Fact has no explanation.

I am not clear on the distinction between logical necessity and brute fact.

For example, there is something that has three sides and is named triangle.

In what sense is "triangle" an explanation of "something that has three sides"?

If not an explanation, then it is a brute fact that a "triangle" is "something that has three sides"

In that case, the Unrestricted PSR is no longer valid.

You apply the thoughts onto the physical world i.e. typing, measuring, hammering, drilling, and driving ... etc. You have ideas how to use and manipulate the physical objects. But the ideas are in your head, not in the world. — Corvus

Ideas are in the head, but ideas can change the world.

If ideas in the brain exist as part of the physical structure of the brain, then this would explain how an idea can change the physical world.

In the same way that an idea physically exists within the brain, numbers, being ideas, would also only exist within the brain in physical form.

I had thoughts, but I wouldn't say the thought existed. You cannot use "exist" on the abstract concepts. — Corvus

If thoughts didn't exist, then how can a thought affect the physical world, such that the thought of pressing the "t" key on the keyboard turns into actually pressing the "t" key on the keyboard.

That sounds like a categorical mistake. It is not matter of real or unreal. It is matter of knowing or not knowing — Corvus

Thoughts exist, otherwise you couldn't have written your post.

Thoughts exist in the physical brain which exists in the physical Universe.

Thoughts must be real otherwise it wouldn't be possible to write posts on the Forum.

That is not what I asked. I asked which version says that it is contingent on our knowing that an event has occurred.............Then you reject every version of the PSR that does not explicitly state that the principle only applies to events we know of.........................It makes an ontological claim. — Fooloso4

There are no definitive versions of the PSR. The PSR is a family of principles.

The PSR is, in fact, a family of principles.......................Variants of the PSR may be generated not only by placing restrictions on the relata at stake (both the explananda and the explanantia), but also on the notion of the relation at stake. (SEP - PSR)

The PSR may be factive, true in actual or possible worlds, or regulative, guiding our study of nature.

Another distinction can be drawn between a factive, as opposed to merely regulative, version of the Principle. A regulative version of the PSR would consider it as a condition for intelligibility (on a par with the Law of Non-Contradiction) and thus as guiding our studying of nature. The factive version simply states that the Principle is true in actuality (or even in all possible worlds). (SEP - PSR)

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How do you know that? — Fooloso4

Principles exist in the mind, not outside the mind.
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Until recently we did not know it existed. We now know it does. According to the PSR it must have a reason for existing. That reason was not created by our discovery of it. — Fooloso4

I can understand a principle that states that we know that things we know about must have a reason, but I find it hard to accept a principle that states that we know that things we don't even know about must have a reason.

Do you know of any argument justifying how we can know that something that we don't even know about must have a reason?

You mean all the science fiction books are real stories? Or merely exist in the authors' minds. — jgill

If a science fiction adventure is being talked about, the science fiction adventure must exist somewhere, whether as print in a book, in the mind of the author or reader or in a world outside any book or mind.

Is a thought in the mind any less real than something in a world outside any mind?

And which of those versions says that it is contingent on our knowing that an event has occurred? — Fooloso4

There is no one definitive version of the PSR.

You interpret the PSR as saying that every event, known or unknown, must have a reason.

It is not a contradiction. An event is something that happens. According to the PSR there is a reason for it happening. Our knowledge of something happening is not a requirement for it to happen. The Webb telescope has detected the earliest known galaxy, JADES-GS-z14-0, which formed about 290 million years after the Big Bang. There is a reason for it happening, whether we know it happened or not. — Fooloso4

I don't believe that the PSR can logically be formulated to apply to unknown events.
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We can now see events that occurred millions of years ago, how does our seeing it now but not previously change what occurred or why it occurred? — Fooloso4

I agree that our seeing an event that occurred millions of years ago doesn't change the original event

It might be that the original event occurred for a reason, or it might be that the original event occurred for no reason. EG, if an event happens where two single objects come together to form two objects, in what sense can the reason for two objects be two single objects.

The Principle of Sufficient Reason is a principle, and principles only exist in the mind.

When the original event happened, the event wasn't following the principle that it could only happen if there was a reason.

As principles only exist in the mind, the mind can only apply principles to things it knows about, meaning that the mind cannot apply principles to things it doesn't know about.

The original event wasn't determined by a Principle. It is only the mind that can determine whether an event followed a Principle, and these can only be events known by the mind.
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We cannot say anything about an event we know nothing about — Fooloso4

I agree when you say that we cannot say anything about an event we know nothing about.

But then you say we can say something about an event we know nothing about, ie, that it must have a reason.

I asked you.................Whose version of the PSR are you relying on?: — Fooloso4

There is no one version of the PSR. There are different formulations. The PSR is a family of principles (SEP - PSR).

For Leibniz, God knows all events whether known or unknown by humans. I am making the case that in the absence of a God, it wouldn't be sensible to apply a PSR to unknown events.

Is there any argument that could explain how we can know something about an unknown event, such as the unknown event having a reason?

So, then, if the first even prime greater than 100 didn't exist I couldn't be writing about it? — Art48

Yes, if the first even prime greater than 100 didn't exist, you couldn't be writing about it.

But you are writing about the first even prime greater than 100, so it must exist.

If something doesn't exist, it is not possible to write about it. If something is being written about, then it must exist somewhere.

Similarly, in the expression "it's said that numbers don't exist", then if something doesn't exist, then how is it possible to write about it.

But you are writing about numbers, so they must exist somewhere, otherwise you couldn't be writing about them.

What is missing in the above is the location of the existence, whether in the mind or in a world outside the mind.

I've seen some YouTube videos where it's said that numbers don't exist. — Art48

If numbers didn't exist, then you couldn't be writing about them, so they must exist somewhere.

I don't propose it. I cite it. — Fooloso4

There are different formulations of the PSR. You cite one version of it. See SEP - Principle of Sufficient Reason.
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The principle is not based on our ability to know the reason, but rather states that there must be a reason. I do not know that there is a reason or that there is not a reason for everything — Fooloso4

A principle that cannot be justified shouldn't be used.

My argument is that if you accept the PRS then you must accept that there is a reason for everything whether that reason is known to us or not — Fooloso4

You propose a formulation of the PSR that states that for everything, whether known or unknown, there must be a reason.

You must feel that there is a justification for this particular formulation.

But do you know of any argument justifying that there must be a reason for things not even known about?

If not, then why accept this formulation?

Since the PSR states that every thing must have a sufficient reason, no exception, then both 2) and 3) would be deniers of the PSR — A Christian Philosophy

You defend the PSR, in that for any thing that exists or is true there is sufficient reason.

Principle of Sufficient Reason (PSR): For any thing that exists or is true, there is a sufficient reason for it to exist or to be true.............We then defend its validity as a first principle — A Christian Philosophy

You also give the examples of things that don't have a sufficient reason, but rather logical necessity, such as "All bachelors are unmarried".

Not all explanations are external to the thing explained. Here are examples of things that are explained by an internal reason, that is, out of logical necessity or inherently. — A Christian Philosophy

Your position seems to fit in with item 2).

We cannot say what that reason is if the thing or event is unknown, but it must have a reason whether we know it or not. — Fooloso4

For Leibniz, God knows all events whether known or unknown by humans.

Can you justify your statement above, in that if an event is unknown to humans then we as humans know that it must have a reason, even if we as humans don't know what the particular reason is.

Is your argument based on the existence of a God?

Are you arguing against the PSR? — Fooloso4

No, I am arguing that the PSR cannot be applied to unknown events

Therefore the PSR cannot be applied to the unknown. — RussellA

If the PSR is valid it should hold for all events whether known or unknown — Fooloso4

I am arguing that it is not possible to know about something that we don't know about, including any reason for the something that we don't know anything about.

There is a reason for it happening, whether we know it happened or not. — Fooloso4

My question is, how is it possible to know the reason for something that we don't know about?

Air is beneficial to folks, but the polluted air also kills folks. So they have the contradictory cases, which makes them unfit for qualifying as acceptable premises which prove the PSR true. — Corvus

I could generalise.

If the PSR was not valid, one day, everything that had been beneficial to life could now be lethal to life, and vice versa.

Could life survive in such a world?

There is a reason for it happening, whether we know it happened or not. — Fooloso4

Philosophically, how is it possible to know something about something we don't know about?

In this particular case, that the something we don't know about has a reason.

Therefore the premises of the reasoning is incorrect or irrelevant, which proves the PSR is not sound. — Corvus

The PSR states that for every fact there is a reason.

If the PSR was not valid, and for every fact there was no reason, then there would be no reason why facts didn't change.

Suppose one day water was beneficial to life and the next day it was lethal, one day air was beneficial to life and the next day it was lethal, one day potatoes were beneficial to life and the next day they were lethal, etc.

Are you saying that life would be able to survive in such a world?

If the PSR is valid it should hold for all events whether known or unknown. — Fooloso4

The expression "all events whether known or unknown" is a contradiction in terms. It is not possible to know that there are unknown events as they are unknown. All that is known are known events.
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If PSR is restricted to what we know or observe then the reason for the star exploding is contingent upon our knowledge of it happening. — Fooloso4

The PSR is a contingent theory in the sense that it states that for every fact there must be an explanation. It doesn't state that every fact is a brute fact.

The PSR is a necessary theory in the sense that for every fact there must be an explanation.

As we don't know what we don't know, the PSR is contingent on what we know.

As regards what we know, the PSR is necessary.

What is the explanation for "for every fact there is an explanation"? — Corvus

Not everyone accepts the PSR, for example Hume. He challenged the PSR and argued that the ideas of cause and effect are distinct, and that we can conceive of an effect without a cause.

But suppose that for every fact there was no explanation. Then equally there would be no explanation why a fact couldn't change. For example, one day it could be a fact that "food is beneficial to humans" and the next day it could be the fact that "food is lethal to humans".

If the PSR was not valid, humans couldn't survive. But humans have survived, Therefore the PSR must be valid.

This sounds like a contradiction. Surely PSR doesn't allow contradictions for the conclusions. — Corvus

PSR - for every fact there is an explanation
Fact = light bends around sources with high mass
Explanation = gravity
There is no contradiction in the explanation.
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These are just repeating the same thing the first part of the sentence using because — Corvus

Yes. "Gravity" is an explanation, but what does it explain?
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Gravity is a scientific concept which must apply to every cases in the universe if it is true. — Corvus

Why does a scientific concept have to be true everywhere?

On Earth the acceleration due to gravity is $9.81\frac{m}{s^2}$ whilst on the Moon it is $1.62\frac{m}{s^2}$

But the light bends around sources with high mass due to gravity. — Corvus

On the one hand "light bends around sources with high mass due to gravity" and on the other hand "gravity causes light to bend around sources with high mass".

In the same way that "the reason he is ambitious is because he is driven" and "the reason the job was complex was because it was complicated."

"Gravity" is more a synonym than a reason why light bends around sources with high mass.

When the light is released into the space, why doesn't it fall to the ground? — Corvus

In a sense it does, as light bends around sources with high mass due to gravity.

From www.astronomy.com

While it is true that photons have no mass, it is also true that we see light bend around sources with high mass due to gravity.

Suppose a star explodes 10 light years from us. It will not be observable to us for 10 years. If the PSR only applies to observable,facts does that mean that with regard to that event the PSR is not valid and will not be valid for 10 years? — Fooloso4

The PSR states that for every event there is a reason

The PSR is valid within certain restrictions.

Prior to the light from the exploding star reaching us, we don't know that there is an exploding star. It is an unknown.

I can certainly imagine a star exploding, but the PSR doesn't apply to the imagination because I can imagine all kinds of impossible things. I can imagine a star exploding for no reason as I can imagine unicorns grazing in Central Park.

Therefore the PSR cannot apply to imagined events.

But what about events that we don't know about. Can I apply the PSR to something unknown. Does every unknown thing have a reason? I can never know because the unknown thing is unknown, and I don't know what to apply the PSR to.

Therefore the PSR cannot be applied to the unknown.

The PSR can be reformulated as "for every observed event there is a reason"

The reason we observed the rock falling is that it fell and we were there to see if fall. There may be various reasons why it fell and various reasons why we were there to see it fall. It does not follow from the fact that we can posit reasons for why we observed the rock fall, that there is a reason for everything. — Fooloso4

True, there are different events.

Let the PSR be that for each event there must be a reason

Situation One - The rock falls, and I see it. There is event A such that I see the rock falling and there is event B such that the rock falls.
Situation Two - The rock falls, but there is no one to see it. There is event C that the rock falls.

Event C
However, as there is no one to observe event C, event C is unknown. As event C is unknown, there can be no discussion as to whether it has a reason or not. Whether unknown event C has a reason or not we can never know, meaning that the PSR for unknown events is unknowable.

Therefore, the PSR is only applicable to observable events.

Event A
The PSR states that there must be a reason why I observe the rock falling.
Assume the PSR is not valid, such that there is no reason why I observe the rock falling.
Then, if I observe a rock falling there would be no reason why I hadn't observed the rock not falling.
But if I had observed the rock not falling, there is no reason why I hadn't observed the rock falling.
But if I had observed the rock falling, there is no reason why I hadn't observed the rock not falling.
If the PSR was not valid, this would lead into an infinite regress.
Therefore, the PSR is valid, ie, there must be a reason why I observe the rock falling.

Event B
The PSR states that there must be a reason why the rock I observe falls.
Assume the PSR is not valid, such that there is no reason why the rock I observe falls.
Then, if the rock I observe falls, then there would be no reason why the rock I observe didn't fall
But if the rock I observe didn't fall, there is no reason why the rock I observe hadn't fallen.
But if I the rock I observe hadn't fallen, there is no reason why the rock I observe didn't fall.
If the PSR was not valid, this would lead into an infinite regress.
Therefore, the PSR is valid, ie, there must be a reason why the rock I observe falls.

In conclusion, the PSR is valid, but only applies to observable facts, events and truths.

Note that "reason" may include a prior explanation, such as "I order a pizza because I was hungry", or contemporaneous ground such as "I order a pizza being hungry".

You did not address the problem. Observing that a rock falls is not a reason for why the rock falls. — Fooloso4

Assume the PSR is not valid

Then, if we observe a rock falling there would be no reason why we hadn't observed the rock not falling.

But if we had observed the rock not falling, there is no reason why we hadn't observed the rock falling.

But if we had observed the rock falling, there is no reason why we hadn't observed the rock not falling.

If the PSR was not valid, this would lead into an infinite regress.

Therefore, the PSR is valid.

What does this mean in terms of PSR? The observation that a rock falls is not a reason for or explanation for it falling. If explanation reaches a dead end then either we have failed to find the reason or there is no reason. — Fooloso4

Using Emilie du Chatelet's argument (SEP - PSR):

P1 - The PSR in the OP states that for any thing that exists or is true, there is a sufficient reason for it to exist or to be true.

P2 - Consider bread. If there was no reason why bread was beneficial to life, there would also be no reason why bread wasn't lethal to life. One day bread could be beneficial and the next day bread could be lethal.

C1 - If the PSR was not valid, humans would be unable to survive in the world.

C2 - As humans do survive in the world, then the PSR must be valid.

But gravity means more than that. — Fooloso4

True, but if a rock never fell to the ground when released, no one would ever have known about gravity.

General relativity remains the framework for the understanding of gravity. The Einstein field equations form the basis of general relativity. The Einstein field equation are based on the cosmological constant. The cosmological constant represents the energy density of space. Nobody really knows what the cosmological constant is exactly, but it is required in cosmological equations in order to reconcile theory with our observations of the universe. (Wikipedia-gravity)

Sooner or later explanations reach a dead end, and we just have to accept our observation that gravity causes a rock to fall to the ground when released, where gravity is something that causes a rock to fall to the ground when released.