Opinionum commenta delet dies, naturae judicia confirmat
Time obliterates the fictions of opinion and confirms the decisions of nature.

A doctor whose breath smells has no right to medical opinion.

But at the same time, there must never be the least hesitation in giving up a position the moment it is shown to be untenable. It is not going too far to say that the greatness of a scientific investigator does not rest on the fact of his having never made a mistake, but rather on his readiness to admit that he has done so, whenever the contrary evidence is cogent enough.

But, as Bacon has well pointed out, truth is more likely to come out of error, if this is clear and definite, than out of confusion, and my experience teaches me that it is better to hold a well-understood and intelligible opinion, even if it should turn out to be wrong, than to be content with a muddle-headed mixture of conflicting views, sometimes miscalled impartiality, and often no better than no opinion at all.

Even if the received opinion be not only true, but the whole truth; unless it is suffered to be, and actually is, vigorously and earnestly contested, it will, by most of those who receive it, be held in the manner of a prejudice, with little comprehension or feeling of its rational grounds

Every variety of philosophical and theological opinion was represented there [The Metaphysical Society], and expressed itself with entire openness; most of my colleages were -ists of one sort or another; and, however kind and friendly they might be, I, the man without a rag of a label to cover himself with, could not fail to have some of the uneasy feelings which must have beset the historical fox when, after leaving the trap in which his tail remained, he presented himself to his normally elongated companions. So I took thought, and invented what I conceived to be the appropriate title of 'agnostic' .

I submit a body of facts which cannot be invalidated. My opinions may be doubted, denied, or approved, according as they conflict or agree with the opinions of each individual who may read them; but their worth will be best determined by the foundation on which they rest—the incontrovertible facts.

If it can't be expressed in figures, it is not science; it is opinion.

It is contrary to the usual practice of professional men to give their opinions upon each other's work unless regularly called upon in the way of their profession.

It is not worth a first class man's time express a majority opinion. By definition, there are already enough people to do that.

Science begets knowledge; opinion, ignorance.

The human understanding when it has once adopted an opinion (either as being the received opinion or as being agreeable to itself) draws all things else to support and agree with it. And though there be a greater number and weight of instances to be found on the other side, yet these it either neglects and despises, or else by some distinction sets aside and rejects, in order that by this great and pernicious predetermination the authority of its former conclusions may remain inviolate.

The influence of Association over our Opinions and Affections, and its Use in explaining those Things in an accurate and precise Way, which are commonly referred to the Power of Habit and Custom, is a general and indeterminate one.

The recipe for perpetual ignorance is: be satisfied with your opinions and content with your knowledge.

There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance.

Though there be no such thing as chance in the world; our ignorance of the real cause of any event has the same influence on the understanding, and begets a like species of belief or opinion.

You have heard of the new chemical nomenclature endeavored to be introduced by Lavoisier, Fourcroy, &c. Other chemists of this country, of equal note, reject it, and prove in my opinion that it is premature, insufficient and false. These latter are joined by the British chemists; and upon the whole, I think the new nomenclature will be rejected, after doing more harm than good. There are some good publications in it, which must be translated into the ordinary chemical language before they will be useful.

You shall yourself be judge. Reason, with most people, means their own opinion.