Leyla,
I see. So, if change is a (logical) conception inferred from a general principle (deduction) rather than a concept deductively and necessarily formed as a result of sensory (not deduced but literal physical) experience (of objects)--that is, derived from experience, what the heck part of that is a posteriori and by what definition of experience?
No. We have the logical concept of experience, right? Experience = the totality of all we experience. When we look within it and perceive things, then the things we perceive are uncertain because they aren't derived directly from the logical concept of experience, but indirectly because the perceptions are merely a subset of the totality of experience. In other words, the concept of experience has been altered by the senses.
So,
a posteriori is a judgement that is derived from experience.
a priori is a judgement that is derived from a definition. "Change" is a judgement (or "change exists", if you like) that is derived from experience.
And, what is this general principle from which you deduce change? It wouldn't be....[drum roll]....that experiences are literally and physically happening?
It's not directly derived from that, because then Kant would have had to equate change with experience, but if that were the case then how could he derive change from it and call it
a posteriori? Defining thing A to be identical as thing B is not the same as deriving A from B. We don't need to deduce jack in that case, just imagine the definition.
The general principle he's using is that if we experience something, then it exists.
If it is, then it seems your understanding looks something like this:
1. (Sensory) experiences are happening but are uncertain since they are empirical.
2. Change is true by observation (that is, by experience--and so is uncertain).
3. Causation has "some empirical element 'mixed up' with it" (that is, experience--and so is uncertain).
Causation is certain here...it is its physical existence that's uncertain because change is uncertain (meaning, not necessary nor universal). But if there is change then there is causation. Causation is certain relative to change.
Now, just in case you want to get peeved over my using the word "relative" to describe a certainty, note that the statement "every change has a cause" addresses every possible location in the universe, because any point is either changing or it's not: if it's changing then it has a cause, and if it's not then no cause is necessary. So, the statement is a universal statement.
4. Therefore, Kant is arguing that there is no such thing as a priori knowledge.
5. Therefore, Kant is arguing that there is no such thing as pure reason (despite the fact that, by definition, deduction itself necessarily implies and proves it.)
Ahhh, no.
Again, I say Kant is saying it is not necessary to experience change for change to be true. It is necessary to experience in order to derive the a priori knowledge "change." The proposition "Every change must have a cause" is impure a priori not because change is experienced (as an object), but because experience (the measurement of objects by sensation and substance) is necessary for its conception.
If that were the reason then that would make all
a priori judgements impure, but clearly that's not relevant. Kant doesn't even appear to include concepts within the realm of experience.
The act of thinking a concept has nothing to do with the meaning of it. Thinking is something that falls into the realm of practical action. Meaning is something wholly logical.
If this were not the case, "Experiences are happening" is equally untrue, unnecessary and not absolute.
Assuming experience and change are identical, which Kant didn't.
What kind of henid a priori reality are you looking for?
We can talk about this when you start making some sense :)