Yes, yes indeed, that's the core of my question, we cannot rely on logic to prove logic valid, so what do we do? We "trust" it because experience suggests its validity?
Yet experience may not always be reliable, not to mention that experience itself may not exist.
You say that logic determines validity but remember that if a camera is broken the photographs too will be flawed.
I "trust" logic, Syllogistic logic on top, and I understand that without logic we can't really think, so taking out logic isn't really gonna get us far, not to mention that, technically, the only answer to my question would need to be illogical, since saving logic with logic is tautologic (it is like saying "that it is because it is") but I'd reject an illogical answer.

I think we might have a bit of problem because of the language differences, but what defines logic?
If logic defines validity, what defines logic? Experience of events maybe? I still can't get it, how do we understand that logic is valid?

Well, that’s a good point, and also brings me to the question: since thinking anything relies on logic, how can we think logic? It would be like building an house on another house built on... what exactly? Since we cannot do without logic, is it an absolute truth or rather an instrument relative to the human mind? If it is the latter, since we are fallible and limited, shouldn’it be so?
The fruit of an apple tree cannot be an orange

Yes, indeed. Logic defines relations of elements, not elements themselves. You asked me how could logic be invalid but I ask you: why couldn’t it?
The validity of statements always depends on the premises, if I say, for example, that killing is right, and Bob killed John, then Bob did right, ok? Logic cannot define elements, just relations of elements, but, how can we prove right or wrong, if we can, those relations? I know I sound redundant and tautologic but is the validity of logic itself ”knowable”? Can we use logic on logic?
I hope you understand my question, I know it’s a bit odd and that I am not the best ad asking it.

All of your answers show a lot of interest, and I appreciate that, and also show me a lot of new things that honestly I didn't know about.
But I think you misunderstand my question, maybe my level of English is not as good as it should be for this, I only meant to bring about a question that may be wrong in its own roots:
Whatever logic you may want to refer to, whatever you prefer to use or even whatever you want to call it, how do you know it is the best tool to analyze relations between things?
I mean, putting aside names and even concepts, whenever you formulate thoughts you must use some kind of logical process, right? Any kind, Jack is a boy, therefore he is not a girl.
So, for those who say that endless logics work on endless different system, which one is to use when?
Because by saying that neither of us can be nor wrong nor right because everyone uses a logic that suits his system and this whole thing makes no sense at all.

For those who say that classical or Syllogistic logic is the one, how do you know?
Most of you agree that there is nothing absolutely true, ontologically I mean, like God for the Christians or The Idea of Good for Plato, yet logic works always and it is always right, thus absolute, how is that? You believe it is.

You bring up a good point, go tell them, they changed the non-contradiction law for this and picked up another one, which is a bit more flexible.

But still, my point was, apart from trusting logic, which still is a question to me, what can we know really?
Can we reduce our knowledge without answering "because yes" to something and stopping there?
We don't really know much, we believe

A Quantum is a particle or a wave?

Well it is clear enough, I understand what you mean but I can't say I agree completely.
My point is that in everyday life we use logic to understand relations of events, the road's wet so it must've rained and if it is very cold outside lakes will freeze. So, if we are presented a relation of events that does not follow that pattern we call it wrong, if you touch ice you do not get burned (I realize these are terrible examples but they'll do)
But you can never use logic on logic, to prove it right nor wrong so can we trust it? And how do we know? Is logic the correct instrument to measure the world around me, if it exists?
What are the limits of it?

My second point, the one you didn't understand was only about trusting logic as an absolute tool a priori, without explanation, as I believe that we cannot express thoughts without one absolute at least.

This is very confused, sorry, I hope you understand

Well there is a bit of A is A but also B but not at the same time, I don't have the preparation to explain it better, I'm sorry, I studied it but my explanation are not exhaustive.

Still, you didn't answer, you believe that things exist in both material and immaterial ways, right?

Anyway the A is A and not B is a bit of a deal with Quantum physics, like ThaMadFool said before, how do we fix it?

I was wondering if that logic can be doubted, if I correctly use it in syllogism for example, will I get the most correct conclusion or one of many possible and neither correct nor wrong conclusions?

So you are sure that there is a material or practical level of existence?
How do you know that?

My point is: is it logical to say that absolute certainty is absolutely uncertain or even impossible?
We are saying that A is A and also B, but it cannot be anything else

But yours are certainties, you are certain that there is no certainty, how is it possible? How do you know?

Yes you are right, I should have been more clear, I was referring to classical logic from Aristotle onwards, so I guess Syllogistic logic and friends, like I wrote to BrianW

Elsewhere, I'm just supposing, you see with the eyes of an empirist or a materialist, Plato's ideas don't exist in a material sense

You mean the laws of nature right?
Even if I were to look at reality with the eye of an empirist or a materialist I'd still have a hard time calling "unyielding" quantum physics.
But by logic I was referring to classical logic, Aristotle's laws, for example, A is A, A is not B and there is not a third option, tertium non datur, and the recent addings like De Morgan's work.

Should have been more precise then, my bad

What you are saying makes sense, but what is knowledge? What can you know surely?
I don't know if you are familiar with Rene Descartes but I based my questions mostly on his solutions.

But if you were trying to say that if you want X you need to do Y, then I agree with you.

P.S. You mentioned gravity, but what if there is nothing outside thoughts and everything we experience is an illusion? What if I don't exist?
Aristotle and Einstein would have wasted their time on an illusion

But again, what is truth and what is better?
Besides, for scientific progress (which I believe you think as ”good”) a lot of things we generally don’t see as moral has been done.

The fact that ethical fundations have nothing to with logic might be arguable but I agree with you.
Yet, I sincerely don’t understand what your point is with the different and incompatible logics.

Well for the second question I assumed classical logic was reliable and went on with it, I was aware of it, I was not trying to prove it right or anything.

As for the other subject I think you raise an interesting issue, since you said that classical logic ran into trouble because of quantum experiments results (and I assume you are referring to the particle wave duality and its implications) I want to ask you: do you think that logic (and if you want philosophy itself) should submit to scientific results?
Because I think there would be a bit of stuff to deal with.
I’m referring to the fact that science holds many philosophical ideas as true and proceeds without explaining them, for example science believes there is something outside thought, which, philosophically, is not certain at all. So, the implications of scientific experiments, which rely on philosophical concepts, can be used to change those philosophical concepts?

P.S. Don’t worry, I’m not trying to prove quantum physics wrong, I’m just asking.