A historian who undertakes to tell his readers what happened is under no obligation to tell them also what could or should have happened, and they may prefer to make up their own minds about that. Thucydides is notably sparing of personal judgements on political and military choice, the significance of an item in a causal sequence, or moral implications. His fullest expression of opinion on a military decision is in vii. 42. 3, where he comments in parenthesis on the view taken by Demothenes of the situation which he found at Syracuse on arrival with the Athenian reinforcements. That we are concerned here with Thucydides’ own opinion, not simply with Demosthenes’, is clear from the finite tenses used throughout the parenthesis; compare viii. 96. 4, where Thucydides dwells on what would have happened if the Peloponnesian fleet in 411 had gone straight for the Piraeus, and contrast the parenthesis ού γἁρ ἃν τὁν ἒκπλουν έπιβουλεῦσαι (vii. 51. 1), in a statement of Syracusan plans. Given that when he wrote vii. 42. 3 Thucydides believed that Nicias and Lamachus ought to have embarked on the investment of Syracuse in the autumn of 415, it seems that he then thought their anxiety over lack of cavalry unjustified. Why did he not say so in vi. 70. 3–71. 2? Again, it is a fair inference from vii. 42. 3 that he then thought Lamachus’ proposal for immediate attack the best of the alternatives discussed by the Athenian generals at Rhegium (vi. 47–51). Perhaps—whatever the order in which he wrote the passages concerned—he changed his mind (cf. p. 15). The principle on which he selected points for comment on what might have been is not intelligible to us; it seems that having made his selection of data for presentation, as it were, in the indicative, he left it to us, for the most part, to construct our own unfulfilled conditionals. This is sometimes easy (e.g. vii. 50. 4).