¹ Lectures and Essays, Vol II (London: Macmillan, 1879). Variously reprinted.

² I say plausible examples, because questions concerning what is uncontroversial on the Clapham omnibus can be extremely controversial in the philosophical lecture-room. Berkeley notoriously maintained that no one but a few philosophers had ever believed in the existence of matter, and my former colleague José Benardete insists that Zeno believed nothing about change and motion that contradicted the beliefs of any of the passengers on the Clapham omnibus. I'll say this: I mean to consider only those philosophical beliefs that are, so to put it, uncontroversially controversial. It will be only these beliefs that will fall within the scope of the question I am asking – whether any philosophical belief is, or ever could be, held by anyone otherwise than upon insufficient evidence.

³ I would say that the negation of a negative belief must be a positive belief, but that the negation of a positive belief will in some cases also be a positive belief. An analogy is perhaps provided by the concept of positive and negative geographical information. That the spy whose whereabouts we should like to know is not in London is a negative piece of geographical information, and that he is in London is a positive piece of geographical information. That he is in the Western Hemisphere is a positive piece of geographical information, but so is the information that he is not in the Western Hemisphere – at least given that he must be either in the Eastern or the Western Hemisphere –, for the latter piece of information narrows down our range of possible specific hypotheses as to his location precisely as effectively as its negation does. I might put my point this way: ‘Theism is false’ is a positive philosophical belief because both theism and its negation, atheism, are philosophical theories or at any rate philosophical positions. ‘Utilitarianism is false’ is not a positive philosophical belief because its negation, non-utilitarianism, so to call it, is not a philosophical theory or position. There are many philosophical theories – many ethical theories – that are incompatible with utilitarianism, but non-utilitarianism, or the disjunction of all ethical theories (indeed, of all propositions) incompatible with utilitarianism, is not one of them: it's incompatible with utilitarianism all right, but it's not an ethical theory – and not a theory of any sort.

⁴ In present-day English, ‘evidence’ is a mass-term: one cannot (now) speak of ‘an evidence’ or ‘evidences’. And there is no corresponding count-noun. Various idiomatic phrases like ‘a piece of evidence’ or ‘a body of evidence’ perform the function of the missing count-noun.

⁵ Despite the negative form of the word ‘incompatible’, I regard this as a clear case of a positive philosophical belief. Any appearance to the contrary is a linguistic accident – for suppose that instead of saying ‘p is incompatible with q’ we used an expression that did not have a negative form (‘p denies q’, perhaps, or ‘p logically excludes q’).

⁶ Philosophical Papers, Vol. II (New York and Oxford: Oxford University Press, 1986), 291–98. The paper first appeared in Theoria 47 (1981), 113–21.

⁷ See Perceiving: A Philosophical Study (Ithaca, N.Y.: Cornell University Press, 1957), 9. and 99–100.