According to one way of speaking, that out of which as a constituent a thing comes to be is called a cause; for example, the bronze and the silver and their genera would be the causes respectively of a statue and a loving0cup According to another the form or model is a cuse; this is the account of what the being would be, and its genera – thus the cuase of an octave is the ratio of two to one, and more generally number – and the parts which come into the account. Again, there is the primary source of the change or the staying unchanged : for example, the man who has deliberated is a cuse, the father is a cause of the child, and in general that which makes something of that which is made, and which changes something of that which something is changed. And again, a thing may be a cause as the end. That is what something is for, as health might be what a walk is for. On account of what does he walk? We answer “To keep fit” and think that, in saying that, we have given the cause.

Suppose one man thought that there are plans because there are leaves, roots, and stems; another that there are leaves, roots and stems because there are plants; a third that there are plants because there are seeds. Aristotle would say that there is no real dipute here, since each party is bringing forward a factor which is explanatory in a different way. The leaves, root, and stem account for the plant in the way in which bronze accounts for a statue, the plant accounts for the leaves, roots, and stem in the way in which health accounts for surgical instruments, and the explanatory role of the seed is in some ways like that of the bronze in the case of the statue, and in some ways like that of the sculptor. We may think that the natural scientist is not in practice likely to need much philosophical assistance of this sort; but philosophers have themselves, perhaps, been misled at times by a feeling that every explanatory factor should be responsible for what is to be explained in the same way, usually in the way in which a murderer is responsible for his victim’s death.
The material cause is characterised as ‘that our of which’. It is what the thing to be explained is made of or can be cut up into.
The formal cause is introduced with the example ‘the ratio of two to one’. In 195a16-21, however, he says that syllables stand to their letters, artefacts to the stuff of which they are make, bodies to fire, etc., wholes to their parts, and conclusions to premises, as their formal cause, and here the formal cause is clearly that which the matter closely constitutes.
The third sort of thing which can be called a cause is a source of change or of staying unchanged. Aristotle’s examples are heterogeneous and some closer to the thing to be explained than others. Art is closer to the statue than the artist and the seed is presumably closer than the father to the child. Strength is said to be the source of change relative to hard work. Presumably, then, moral states, virtues and vices, would be sources of change relative to voluntary actions and closer sources than the deliberate agent. That being so, it is misleading to call Aristotle’e sources of change efficient causes. Aristotle says that actual causes are always contemporaneous with the things for which they are responsible, not antecedent.
Finally there is the end. This we are told, is what the other things are for, and the best thing. ‘The other things’ sounds a vague phrase, but may be taken fairly literally. Noot only are the organic parts and natural behaviour of living things, according to Aristotle, for something, but also dispositions, like strength and medical knowledge, are for thigns, for hard work or health.
That arts and artefacts have objectives which are in some sense goods may be generally agreed; but Aristotle particularly hopes to find, outside the sphere of rational action, factors which are ends in the same sense of being what is best and what other things are for: can this be seen otherwise than as a foolish mistake?
Aristotle suggests that wherever we have a continuous process of change, its end is what it is for. For example, the process of shipbuilding is for the ships in which it terminates, rather than the other way around. However it is not much use, first because even if a process is rather for its end than the end for the process, still it might be that neither is for the other, and second because as Aristotle himself observes, processes may end in bad states such as death or disease; we cannot establish what a process is for just by observing where it ends, but must know independently what ‘the best’ end for it is.
Besisdes ends of processes, however, Aristotle speaks of ends of physical objects, and the end of a physical object is its work or function; can he establish that things other than artefacts have functions, and then argue that performing its function is what is best for a thing and what its parts, dispositions, etc, are for?
Aristotle defines the natural purpose of a thing as that for which the prudent man as such, and the appropriate knowledge, would use it. This however is unhelpful, for how would a prudent man use a tiger for example, and may not even be intended to apply to anything but artefacts.
So much on the four senses in which, according to Aristotle, a thing can be called a cause or said to be responsible for something. Thigns are called causes in any one of these sense, not because they have something in common, or because they conform to a single definite idea, but by analogy: we have no single idea answering to any of the expressions ‘matter’, ‘form’, ‘source of change’, ‘end’, and their meaning must be grasped in the way outlined above.