It is in the applications of this view that we come to what must be regarded as downright fallacies.If,as Mill holds,an effect may be something absolutely disparate from the cause --a new thing which starts into existence when its antecedent occurs --we are led to another result.There is,then,no apparent reason why the same thing should not spring up in answer to different summonses.Not only is this possible,but,as Mill thinks,it constantly occurs.This is his doctrine of the 'Plurality of Causes.'A given cause,he holds,can only produce one effect.But a given effect may follow various causes.So long as the relation is merely one of arbitrary succession,not of continuity,this is obviously possible.The fully scientific view,I take it,would be that when we speak of 'cause and effect'we are really thinking of a single process regarded in different ways.We may analyse the process differently for different purposes,and infer the past from the future or the future from the past;but we assume that,if we could perfectly understand the whole process,there would be thorough continuity,and no abrupt supersession of one thing or one set of 'laws'by another.This continuity is precisely what Mill systematically denies.A cause,he holds,means an absolute beginning of a new effect.(70)The process becomes a series of distinct terms --a set of 'links'in a chain,not a flow of a stream.One remarkable case is enough to illustrate the point.When Bacon's claims to have founded a truly scientific theory are considered,it is generally said that his guess as to the nature of heat is a point in his favour.(71)Mill,however,takes this particular case as an instance of Bacon's errors.Bacon,he says,(72)'entirely overlooked the Plurality of Causes.All his rules imply the assumption,so contrary to what we now know of nature,that a phenomenon cannot have more than one cause.'Bacon was misguided enough to apply this to heat.Now,as Mill had already argued,heat may have several causes:the 'sun,'or 'friction,'or 'percussion,'or 'electricity,'or 'chemical action.'(73)Consequently,the attempt to find a single cause is doomed to failure.We shall find,not that one antecedent but,that one of several antecedents is always present.Clearly the 'sun'is not 'friction,'nor is 'percussion''electricity.'Each of those phrases indicates concrete facts involving various processes.
Heat,as a 'mode of motion,'occurs in them all,because all involve particular phases of movement.From the 'raw'fact,as it presents itself --'This body is hot'--I cannot say which of various laws represents the true antecedents in that case.The heat may have been caused by exposure to fire or by friction.In that sense,undoubtedly,one effect may really have any number of 'causes.'But replace all the conditions,and it is evident that there can be only one true analysis of the whole process.
