But a difficulty arises when a similar method is applied to a doctrine sincerely disputed.To the statement,'this is a necessary belief,'it is a sufficient answer to reply,'I don't believe it.'In that case,an intuition merely amounts to a dogmatic assumption that I am infallible,and must be supported by showing its connection with beliefs really universal and admittedly necessary.
Dugald Stewart followed Reid upon this main question,and with less force and originality represents the same point of view.He accepts Reid's view of the two co-ordinate departments of knowledge;the science of which mind,and the science of which body,is the object.Philosophy is not a 'theory of knowledge'or of the universe;but,as it was then called,'a philosophy of the human mind.''Philosophy'is founded upon inductive psychology;and it only becomes philosophy in a wider sense in so far as we discover that as a fact we have certain fundamental beliefs,which are thus given by experience,though they take us in a sense beyond experience.Jeffrey,reviewing Stewart's life of Reid,in the Edinburgh Review of 1804,makes a significant inference from this.Bacon's method,he said,had succeeded in the physical sciences,because there we could apply experiment.But experiment is impossible in the science of mind;and therefore philosophy will never be anything but a plaything or a useful variety of gymnastic.Stewart replied at some length in his Essays,(25)fully accepting the general conception,but arguing that the experimental method was applicable to the science of mind.Jeffrey observes that it was now admitted that the 'profoundest reasonings'had brought us back to the view of the vulgar,and this,too,is admitted by Stewart so far as the cardinal doctrine of 'the common sense'philosophy,the theory of perception,is admitted.
From this,again,it follows that the 'notions we annex to the words Matter and Mind are merely relative.'(26)We know that mind exists as we know that matter exists;or,if anything,we know the existence of mind more certainly because more directly.The mind is suggested by 'the subjects of our consciousness';the body by the objects 'of our perception.'But,on the other hand,we are totally 'ignorant of the essence of either.'(27)We can discover the laws either of mental or moral phenomena;but a law,as he explains,means in strictness nothing but a 'general fact.'(28)It is idle,therefore,to explain the nature of the union between the two unknowable substances;we can only discover that they are united and observe the laws according to which one set of phenomena corresponds to the other.From a misunderstanding of this arise all the fallacies of scholastic ontology,'the most idle and absurd speculation that ever employed the human faculties.'(29)The destruction of that pseudo-science was the great glory of Bacon and Locke;and Reid has now discovered the method by which we may advance to the establishment of a truly inductive 'philosophy of mind.'
It is not surprising that Stewart approximates in various directions to the doctrines of the empirical school.He leans towards them whenever he do es not see the results to which he is tending.Thus,for example,he is a thorough-going nominalist;(30)and on this point he deserts the teaching of Reid.He defends against Reid the attack made by Berkeley and Hume upon 'abstract ideas.'Rosmini,(31)in an elaborate criticism,complains that Stewart did not perceive the inevitable tendency of nominalism to materialism.(32)Stewart,in fact,accepts a good deal of Horne Tooke's doctrine,(33)though calling Tooke an 'ingenious grammarian,not a very profound philosopher,'but holds,as we shall see,that the materialistic tendency can be avoided.
As becomes a nominalist,he attacks the syllogism upon grounds more fully brought out by J.S.Mill.Upon another essential point,he agrees with the pure empiricists.He accepts Hume's view of causation in all questions of physical science.In natural philosophy,he declares causation means only conjunction.The senses can never give us the 'efficient'cause of any phenomenon.
In other words,we can never see a 'necessary connection'between any two events.He collects passages from earlier writers to show how Hume had been anticipated;and holds that Bacon's inadequate view of this truth was a main defect in his theories.(34)Hence we have a characteristic conclusion.He says,when discussing the proofs of the existence of God,(35)that we have an 'irresistible conviction of the necessity of a cause'for every change.
Hume,however,has shown that this can never be a logical necessity.It must then,argues Stewart,be either a 'prejudice'or an 'intuitive judgment.'
Since it is shown by 'universal consent'not to be a prejudice,it must be an intuitive judgment.Thus Hume's facts are accepted;but his inference denied.The actual causal nexus is inscrutable.The conviction that there must be a connection between events attributed by Hume to 'custom'is attributed by Stewart to intuitive belief.Stewart infers that Hume's doctrine is really favourable to theology.It implies that God gives us the conviction,and perhaps,as Malebranche held,that God is 'the constantly operating efficient Cause in the material world.'(36)Stewart's successor,Thomas Brown,took up this argument on occasion of the once famous 'Leslie controversy';and Brown's teaching was endorsed by James Mill and by John Stuart Mill.