 The subject of Theophrastus’ take on Aristotle’s teleology has been at the centre of contemporary scholarship. Theophrastus’ Metaphysics refers to passages in Aristotle’s writings that reveal him struggling to explain certain phenomena in terms of his teleological principle, when it may have been better for him to admit that such explanations are simply inappropriate. For instance, Theophrastus claimed that natural phenomena such as extremely dry and moist seasons, the size of the deer’s horns, or the insects that only live for a day seem to violate the principle that all things in nature are for the sake of something. He thus suggested that such instances should urge us to question whether teleological reasons should be put forward in all cases without qualification, as well as to acknowledge that there may be limits to the determination of causes. This does not mean, however, that Theophrastus failed to recognize the role of necessity in nature nor that he rejected all teleological explanations, though it is true that in his surviving works there are few such examples. So, his attitude in this issue should rather be interpreted as showing nothing but caution towards an indiscriminate application of the principle that nature does nothing in vain (see Lennox 1985; Repici 1990; van Raalte 1993: 491–2; Gourinat 2015).