Is a priori logic immutable with the passage ot time?

If a certain knowledge is a priori, does it follow that that knowledge has always been and will always be a priori knowledge by definition?

For example, it is the case that the phrase, “All husbands are men” is a priori. Is it then the case that the phrase “All husbands are men” will always be an a priori? is there ever a case in time in which such an a priori phrase would not be a priori?


i have always had a strange idea of what a priori knowledge or logic is.

i have alwaysed used the example of 1+1=2

so will it always be true that 1+1=2?

it will always be true that if you have 1 apple and add another apple then you will have “two” apples.

Note that the statement 1+1=2 is correct in the a priori sense and also in an earthly sense. that is, we understand the language.

In the case of all husbands being men, It is not so much a logical deduction as it is a statement of the way the world is, or more specifically, the way our languae defines the subject.

In the english language “husband” is the term we use to describe a male partner.

If we change the definition of the english language then that statement would not hold true, but also if we change the math language 1+1 might not equal 2.

I could question your very example. What makes you think that “all husbands are men” is a priori?

“husband” is a subjective term is it not? monogomy is also a subjective term.

Here’s how my mind resolves the dilemma.

I can say that 1 and 1 apples are 2 apples, regardless if the language changes it will always be “right”.

To say the word “husband” is actually to say “male partner”


All male partners are male.

So your supposition is litterally contained within the terms defined.

It’s like me saying that all spheres are round.

a priori logic is not suppose to change… this we can be sure.

the statement “male partners are male” will not change with time.

But if we look at it in terms of an observation (NOT A PRIORI), the term husband extits AS WE DEFINE IT.

it is possible that in the future we will call female partners “husbands” for one reason or another.

we might even become omnisexual, try to imagine that :laughing:

in this case, husband is as husband IS, but what you must remember is the difference between saying that “all husbands are male” and “all male partners are male”.

“all husbands are male” remains a priori only if the language in which it is asserted clearly defines “husband” as a “male partner” otherwise that’s like me saying all phone numbers consist of 7 digits and an area code, this will undoubtedly change with time, besides the fact that it is not a priori.

does this clear anything up?

Yes, you have certainly helped me, but I do have a follow up question.

If mathematics is composed of a priori logic and deductions from that, is it the case that mathematics, regardless of the language used, is also immutable with time?

mathematics and every other thing derived through a priori logic do not exist a posterori… they cannot be sensed.


Does that mean that mathematics cannot ever change as time progresses? (or that it was ever different in some way in the past)?

Apologies if I am being unreasonably dense. I am new to philosophy.

no, mathematics changes with definitions… but that’s all it ever is… definitions… (and therefore arbitrary)

mathematics isn’t an actually existing tangible thing…


Okay, I know I’m beating the dead horse now, BUT… given the basic axiom that x=x, could it ever be the case that the logic derived from that could ever be different? Or for a more specific example, is it the case the relation 2 + 2 = 5 ever be true? Or, is it that case that 2 + 2 = 5 can be true at the same time that 2 + 2 = 4 is true?

Or maybe I could ask about this classic: can the concept of a four sided triangle ever be logically sound? (can there exist a four sided triangle, either in reality or thought only?)

I know this is kind of imprecise, but hopefully I can eventually come to a correct understanding.

Thanks for your patience!


Our definitions of math changes, but the quantitative logic used is universal and a priori.

the language is always subject to change, and even the way we use certain bits of logic, but the logic cannot change with time as far as we know.

no, the rules of logic can change like the rules of any other game…


no those are just different rules.

no, they are different games…


humans choose the rules to create the game. the game is aposteriori, the rules individually are a priori and do not cease to exist if we change them. sure noone will be there to percieve of them but they were never really that tangeable in the first place.

a priori logic exists the same way until we make it tangeable.

Presumably a priori logic could exists without humans (beside the fact logic wouldn’t)

to reiterate a typo mangles post.

the idea of 1 thing and another thing making 2 things in total is a possibility that existed even if we imagined it or not.

when we die it will not cease to exist without is to employ it. the logic used in the deduction is considered a priori.

we humas might change the way we use logic or even come to a higher understanding, but the way we once used 1+1=2 will never change.

the past does not exist.


the past does not not exist.

show it presently to prove it


Touché, but an appeal to ignorance is no proof for your claim.

2+2=5 can be true if we equivocate between sets and members of them.

that’s only changing the symbols, not the meaning.