To we humans (if you're
a dog reading this, kudos), the accuracy of the human mental
process is not identifiable, as it is the human mental process
that tests and makes the judgment of the accuracy. If your goal
is to determine if the human mental process is 100% percent reliable,
that means you do not know if your means of testing (human mental
process) is 100% reliable, which makes it impossible to determine
if the human mental process is 100% reliable.
There are countless examples of unreliability in the human
mind: the Muller-Lyer and other illusions,
inborn and learned biases that effect how you and I perceive
objects, numerology. These demonstrate that the human mental
process cannot be considered 100% reliable.
One's opinion on the reliability the human mind involves leaps
of faith and unprovable assumptions.