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Kant - The Critque of Pure Reason

Human reason, in one sphere of its cognition, is called upon to
consider questions, which it cannot decline, as they are presented
by its own nature, but which it cannot answer, as they transcend every
faculty of the mind.

It falls into this difficulty without any fault of its own. It
begins with principles, which cannot be dispensed with in the field
of experience, and the truth and sufficiency of which are, at the same
time, insured by experience. With these principles it rises, in
obedience to the laws of its own nature, to ever higher and more
remote conditions. But it quickly discovers that, in this way, its
labours must remain ever incomplete, because new questions never cease
to present themselves; and thus it finds itself compelled to have
recourse to principles which transcend the region of experience, while
they are regarded by common sense without distrust. It thus falls into
confusion and contradictions, from which it conjectures the presence
of latent errors, which, however, it is unable to discover, because
the principles it employs, transcending the limits of experience,
cannot be tested by that criterion. The arena of these endless
contests is called Metaphysic.

...We come now to metaphysics, a purely speculative science, which
occupies a completely isolated position and is entirely independent
of the teachings of experience. It deals with mere conceptions--not,
like mathematics, with conceptions applied to intuition--and in it,
reason is the pupil of itself alone.

...This critical science is not opposed to the dogmatic procedure of
reason in pure cognition; for pure cognition must always be
dogmatic, that is, must rest on strict demonstration from sure
principles a priori--but to dogmatism, that is, to the presumption
that it is possible to make any progress with a pure cognition,
derived from (philosophical) conceptions, according to the
principles which reason has long been in the habit of employing--
without first inquiring in what way and by what right reason has
come into the possession of these principles. Dogmatism is thus the
dogmatic procedure of pure reason without previous criticism of its
own powers, and in opposing this procedure, we must not be supposed
to lend any countenance to that loquacious shallowness which arrogates
to itself the name of popularity, nor yet to scepticism, which makes
short work with the whole science of metaphysics.

... The Human Intellect, even in an Unphilosophical State,
is in Possession of Certain Cognitions "a priori".

... But, for the present, we may content ourselves
with having established the fact, that we do possess and exercise a
faculty of pure a priori cognition; and, secondly, with having pointed
out the proper tests of such cognition, namely, universality and
necessity.

----
Even Kant struggled with this question
The presence of a reasoning facility is accepted "a priori"
Stating this, he still cannot state how we came to possess it or
what it is, only that it is present and logical and is useful in understanding
----