The structure of propositions is analysed by Aristotle into two chief components, the subject and the predicate. The subject is that about which something true or false is asserted; the predicate is what is asserted about the subject.

Aristotle’s account of change turns on the idea of potentiality (in Greek dunamis, from which we get the word ‘dynamic’). Substances have a potentiality either to be changed by something acting on them, which is ‘passive potential’, or to cause change in other substances, which is what animate things can do because they possess ‘active potential’.

What is ‘the function of human beings’? Aristotle approaches an answer to this question by analogies. What makes a good flute-player? Skill at playing the flute. A good carpenter? One good at making things from wood. Each is ‘good’ because he performs his particular function, his work (ergon), well. To do his work well is the virtue or excellence

Practical philosophy is one thing: it is politics, of which ethics is an integral part. ‘Politics’ means the study of the polis – the state – and since the state is the society of people who constitute it, ethics and politics are continuous with each other. You might say that Aristotle thought of politics as ‘the theory of conduct’ in general. In

a human being can acquire something analogous to a technical skill in knowing how to navigate between the vicious extremes between which the mean is the associated virtue.

In the Nicomachean Ethics he begins by noting that every pursuit aims at some good, which means that there are as many different kinds of good as there are pursuits. Such things as boat-building, military strategy and getting rich each requires subordinate goods to be attained – in carpentry, sword-making, starting a business – each of which has

And what is that end which is desirable for its own sake? There is ‘very general agreement’ about this, Aristotle says; both ‘the general run of men and people of superior refinement say that it is happiness’ (eudaimonia). (‘Happiness’ is an inadequate translation of this term: ‘well-being and well-doing’, ‘flourishing’, would be better.)

So now we must understand the nature of virtue. There are two kinds of virtue, says Aristotle: those of mind, and those of character. The virtues of mind further subdivide into ‘practical wisdom’ and ‘theoretical wisdom’.

Virtues of character include courage, temperance and justice.