The agreed fact was caused by A5

5 A more complex kind of case is that where we know that the cause was A or B, and that A and B were both true, yet we still wish to determine which was the actual cause (e.g. we might know that the patient's death was caused by either heart disease or liver disease, and that both his heart and liver were diseased). But we shall not discuss these sorts of cases here.

Normally P2 will be backed by a covering generalisation, of the form 'Whenever such-and-such happens, it is caused by . . .'. But not always; sometimes we know what the possible causes of a given fact or event are, but are unable to articulate generalisations from which they may be inferred. In cases where we do know the appropriate generalisations, however, we should, as always, include them in the reconstruction. That is what we did in the plant example. Of course the list of possible causes listed in P2 may be of any length.6

The generalisations appealed to in arguments of this kind are often soft rather than hard. For example, a sudden increase in the temperature of an automobile engine's cooling system is usually, but not always, caused either by a leak in the cooling system or a broken fan belt. In such cases, we must insert 'usually', or 'probably', or some suitable variant, into the appropriate place in P2. Likewise, we may not be able to rule out with certainty the possible explanations listed in P3. Again, in such cases we should have to insert 'probably', 'usually', or some suitable variant, into the appropriate place in P3 (or perhaps 'probably not', etc.). In these cases the arguments will be inductive rather than deductive. Such an argument might look like this:

P1) The temperature of the engine's cooling system has suddenly increased. P2) Almost always, a sudden increase of the temperature of an engine's cooling system is caused by a broken fan belt, or a leak in the cooling system. P3) It is very unlikely that the fan belt has broken.

C) Probably, the increase of the temperature of the engine's cooling system was caused by a leak in the cooling system.

In this case, P3 might be the conclusion of another argument; for example it may have been inferred from the fact that the fan belt is new.

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