Opinions are in the mind. They're beliefs about how things are in the world. That is, they're beliefs, or judgments, about what the facts are. The facts are objective states of affairs that exist regardless of our opinions (unless they're facts about opinions). The facts are facts regardless of whether we're aware of them. An opinion is true (or factual) if it accurately reflects the facts; otherwise, an opinion is false.Since opinions are beliefs, and since beliefs that are true and that are rationally justified in the right way (or, perhaps, that were brought about in the right way) count as knowledge, some opinions can become knowledge. Take an opinion, add truth and enough justification (of the right sort) and, voila, you've got knowledge.
This interpretation of the key terms is consistent with some historical evidence concerning their use. For instance, via the Oxford English Dictionary (OED; not the open-access edition), I found the following nugget from John Milton:
Opinion in good men is but knowledge in the making. (Milton, Areopagitica, 1644)What they now opine, they may some day know. Once they've acquired the knowledge, we may say that their old opinion is not just an opinion but, also, genuine knowledge. Or, if we prefer to treat knowledge and opinion as mutually exclusive categories, we may say that their old opinion is no longer an opinion but is, instead, knowledge. We'll incline towards this latter approach if we use 'opinion' as short for mere opinion or if we're enamoured of the ancient Greek distinction between doxa and episteme. Regardless, we may then contrast opinion with knowledge in something like the way that Thomas Reid does in this passage:
Knowledge, I think, sometimes signifies things known; sometimes that act of the mind by which we know them. And in like manner opinion sometimes signifies things believed; sometimes the act of the mind by which we believe them. ... In knowledge, we judge without doubting; in opinion, with some mixture of doubt. (Reid, Essays on the Intellectual Powers of Man, Essay VI 'Of Judgment', Ch. I ['Of Judgment in General'], sec. iii, 1785)Reid isn't using the terms exactly as I did in my quick and dirty account, for here (at least) he puts the knowledge-opinion distinction chiefly in psychological terms; opinion sounds like a more tentatively held belief.* Still, the contrast is between opinion and knowledge, not between opinion and fact. What would be the point of opting for the latter juxtaposition? After all, opinions are mental states, but facts are what those states purport to be about and are not, themselves, mental states.
So, my quick and dirty interpretation is roughly in sync with the above excerpts from Reid and Milton. In addition, it accords with the following quotation of John Locke, who also contrasts opinion with knowledge:
It is therefore worth while to search out the bounds between opinion and knowledge; and examine by what measures, in things whereof we have no certain knowledge, we ought to regulate our assent and moderate our persuasion. ... I shall make some inquiry into the nature and grounds of faith or opinion: whereby I mean that assent which we give to any proposition as true, of whose truth yet we have no certain knowledge. (Locke, Essay Concerning Human Understanding, Book I, ch. i, paragraph 3, 1689)Here, to hold an opinion is to take something to be true; and this taking, while not 'yet' certain, is at least susceptible of rational support (and critique). All three of the above-quoted authors use 'opinion' in this fashion.
It looks like somewhere along the way, 'opinion' took on another interpretation, one that exempted the opinion-holder from rational accountability. This conjecture is suggested by a 19th-Century article in the Spectator about Lord John Russell (Bertrand Russell's grandfather). The article, called 'Odd Habit in a Leading Statesman' (Feb. 17, 1849), quotes Lord John as saying,
I am told, 'you then [in 1846] opposed coercion, and you now propose it yourself.' It is quite true that I am liable to that charge. All I can say is, that I thought that bill was not adapted to the circumstances of the time .... But that, again, is entirely a matter of opinion. Those who differ from me may hold the reverse view. (Spectator, Feb. 17, 1849, p. 10)Russell's critics then opine:
It may almost be said that Lord John Russell never gives a reason in support of his 'opinion'; for he uses that word in the vulgar sense, to mean an impression which is not to be accounted for beyond its bare enunciation. ... How is it that Lord John cannot state the elements of his opinion and the grounds of his judgment,—describe the circumstances in 1846, and show in what the bill of that year failed to fit them...? We do not say that Lord John has not elements for his opinion or grounds for his reason; but it is not 'condensation' of oratory to omit all statement of them, any more than an impression unsupported by distinctly explained reasons is to be accepted as a well-grounded and matured, a 'wise' opinion. Lord John, as a man, has a right to his own opinion, or even to his own unexplained impressions; but few men have been allowed to retain offices of trust who have so steadily fallen into the habit of not stating reasons for what they do. (Ibid., [Emphasis added])Once more, we see that 'opinion', in its established, centuries-old use, was not meant to preempt any call for rational critique. Interestingly, we see also that the word had taken on a 'vulgar', second sense in which it was apparently meant to do just that.
The word 'fact' has undergone more changes in meaning, which I'll examine in subsequent posts. For now, I'll note that I follow Barbara J. Shapiro (in Culture of Fact: England, 1550–1720 [Cornell University Press, 2000]) in saying that the legal use of 'fact' set the course for that term's use beyond the law and especially in the sciences. Shapiro marshals much evidence having to do with Sir Francis Bacon, but I don't know if she adduces the following quotation (from 1605):
This facility of credit and accepting or admitting things weakly authorised or warranted, is of two kinds according to the subject: for it is either a belief of history (as the lawyers speak, matter of fact); or else of matter of art and opinion. (Bacon, 'The Advancement of Learning', Book I, iv, paragraph 9, 1605)Bacon, lawyer and excogitator on scientific method, here introduces the phrase 'matter of fact' as a technical term from the law. In that domain, it contrasts with matters of law.
Consider the following way of marking the contrast between matters of fact and matters of opinion, which is drawn from an influential, 19th-Century textbook. The book is Elements of Rhetoric by Richard Whately. According to Bishop Whately,
By a 'Matter of Fact' is meant, something which might, conceivably, be submitted to the senses; and about which it is supposed there could be no disagreement among persons who should be present, and to whose senses it should be submitted; and by a 'Matter [or Question] of Opinion' is understood, anything respecting which an exercise of judgment would be called for on the part of those who should have certain objects before them, and who might conceivably disagree in their judgment thereupon. ... [I]t is not meant ... that there is any greater certainty ... in the one case than in the other. [For example,] [t]hat one of Alexander's friends did, or did not, administer poison to him, every one would allow to be a question of fact; though it may be involved in inextricable doubt: while the question, what sort of an act that was, supposing it to have taken place, all would allow to be a question of opinion; though probably all would agree in their opinion thereupon. (Whately, Elements of Rhetoric, 7th edition, ch. II, sec. 4, p. 52 [pp. 58-9 in the English edition published by Fellowes], 1846)Whately's conception of matters of fact is consonant with the one that one finds in the law. Also, Whately takes one's view on a matter of opinion to be a truth-claim, where there may be more certainty regarding the claim's truth than there is for a belief about a matter of fact. In his example, as long as we lack good evidence, our beliefs about whether Alexander's friend poisoned poor Alex remain mere opinions (about a matter of fact). This use of 'opinion' fits with the above characterizations offered by Reid and Locke -- opinions suffer from doubt or a lack of certainty. But our conviction that it's wrong to poison one's friend is held with more certainty. Indeed, we may feel no doubt on the matter. One who adopts Reid's understanding of the knowledge-opinion divide would, then, conclude that this moral conviction is knowledge of a moral fact, but I think Whately would still classify it as an opinion -- a correct, rational one, but an opinion nonetheless.
*[Note Added on June 6: While Reid there pitches the knowledge-opinion distinction in seemingly psychological terms, his more considered formulations put the difference in an epistemological way. E.g., he says that opinion 'stands upon a weaker foundation, and is more liable to be shaken and overturned' than knowledge. In accordance with an epistemological formulation such as this, Reid can say that while one might not actually harbour doubts about a belief, one ought to (owing to its weaker foundation -- of which one might be unaware), and this is what makes it a mere opinion rather than knowledge. On this account, a Reidian (and Lockean) on the knowledge-opinion distinction might say that in Whately's example, one who feels no doubt concerning a belief about morality perhaps ought to feel some doubt, since the belief has a weaker foundation, which would make the belief an opinion only.]