8. I. Doubtful propositions taken for principles.
I. The first and firmest ground of probability is the conformity
anything has to our own knowledge; especially that part of our knowledge which we have embraced, and continue
to look on as principles. These have so great an influence upon our opinions, that it is usually by them we judge of
truth, and measure probability; to that degree, that what is inconsistent with our principles, is so far from passing
for probable with us, that it will not be allowed possible. The reverence borne to these principles is so great, and
their authority so paramount to all other, that the testimony, not only of other men, but the evidence of our own
senses are often rejected, when they offer to vouch anything contrary to these established rules. How much the
doctrine of innate principles, and that principles are not to be proved or questioned, has contributed to this, I will
not here examine. This I readily grant, that one truth cannot contradict another: but withal I take leave also to say,
that every one ought very carefully to beware what he admits for a principle, to examine it strictly, and see
whether he certainly knows it to be true of itself, by its own evidence, or whether he does only with assurance
believe it to be so upon the authority of others. For he hath a strong bias put into his understanding, which will
unavoidably misguide his assent, who hath imbibed wrong principles, and has blindly given himself up to the
authority of any opinion in itself not evidently true.
