LOGIC all its past tense, is not really a proposition about the past But this solution is nowhere clearly enunciated by Aristotle, and the problem he set out recurred in many diVerent forms in later antiquity and in the Middle Ages.8 In the Prior Analytics Aristotle explores the possibility of constructing syllogisms out of modal propositions His attempt to construct a modal syllogistic is nowadays universally regarded as a gallant failure; and even in antiquity its faults were realized His successor Theophrastus worked on it and improved it, but even so it must be regarded as unsatisfactory The reason for the lack of success has been well explained by Martha Kneale: it is Aristotle’s indecision about the best way to analyse modal propositions If modal words modify predicates, there is no need for a special theory of modal syllogisms For these are only ordinary assertoric syllogisms of which the premises have peculiar predicates On the other hand, if modal words modify the whole statements to which they are attached, there is no need for a special modal syllogistic, since the rules determining the logical relations between modal statements are independent of the character of the propositions governed by the modal words.9 The necessary basis for a modal logic, she concludes, is a logic of unanalysed propositions such as was developed by the Stoics This statement needs qualiWcation It is true that the Xowering of modal logic in the twentieth century depended on just such a propositional calculus But there were also signiWcant developments in modal logic in the Middle Ages within an Aristotelian context, when Aristotle’s own modal syllogistic was superseded by much more sophisticated systems Again, not all propositions in which words such as ‘can’ and ‘must’ occur within the predicate can be replaced by propositions in which the modal operator attaches to an entire nested proposition ‘I can speak French’, for instance, does not have the same meaning as ‘It is possible that I am speaking French’ Aristotle makes a distinction between two-way possibilities (such as a man’s ability to walk, or not to walk, as he chooses) and one-way possibilities (Wre can burn This passage of the de Interpretatione has also been the subject of voluminous discussion in modern times My interpretation owes a lot to that of G E M Anscombe, whose ‘Aristotle and the Sea-Battle’ of 1956 (From Parmenides to Wittgenstein (Oxford: Blackwell, 1981) ) is still, nearly Wfty years on, one of the best commentaries on the passage For a carefully argued alternative account, see S Waterlow, Passage and Possibility: A Study of Aristotle’s Modal Concepts (Oxford: Clarendon Press, 1982), 78–109 Kneale and Kneale, The Development of Logic, 91 135