What was required to escape from it?According to Kant,nothing less than a revision of Descartes'mode of demarcation between object and subject.
The 'primary qualities'do not correspond in this way to an objective world radically opposed to the subjective.Space is not a form of things,but a form imposed upon the data of experience by the mind itself.This,as Kant says,supposes a revolution in philosophy comparable to the revolution made by Copernicus in astronomy.We have completely to invert our whole system of conceiving the world.Whatever the value of Kant's doctrine,of which I need here say nothing,it was undoubtedly more prolific than Reid's.Reid's was far less thoroughgoing.He does not draw a new line between object and subject,but simply endeavours to show that the dilemma was due to certain assumptions about the nature of 'ideas.'The real had been altogether separated from the phenomenal,or truth divorced from fact.You can only have demonstrations by getting into a region beyond the sensible world;while within that world --that is,the region of ordinary knowledge and conduct --you are doomed to hopeless uncertainty.An escape,therefore,must be sought by some thorough revision of the assumed relation,but not by falling back upon the exploded philosophy of the schools.Reid and his successors were quite as much alive as Locke to the danger of falling into mere scholastic logomachy.They,too,will in some sense base all knowledge upon experience.Reid constantly appeals to the authority of Bacon,whom he regards as the true founder of inductive science.The great success of Bacon's method in the physical sciences,encouraged the hope,already expressed by Newton,that a similar result might be achieved in 'moral philosophy.'(21)Hume had done something to clear the way,but Reid was,as Stewart thinks,the first to perceive clearly and justly the 'analogy between these two different branches of human knowledge.'The mind and matter are two co-ordinate things,whose properties are to be investigated by similar methods.Philosophy thus means essentially psychology.The two inquiries are two 'branches'of inductive science,and the problem is to discover by a perfectly impartial examination what are the 'fundamental laws of mind'revealed by an accurate analysis of the various processes of thought.
The main result of Reid's investigations is given most pointedly in his early Inquiry,and was fully accepted by Stewart.Briefly it comes to this.No one can doubt that we believe,as a fact,in an external world.We believe that there are sun and moon,stones,sticks,and human bodies.This belief is accepted by the sceptic as well as by the dogmatist,although the sceptic reduces it to a mere blind custom or 'association of ideas.'Now Reid argues that the belief,whatever its nature,is not and cannot be derived from the sensations.We do not construct the visible and tangible world,for example,simply out of impressions made upon the senses of sight and touch.To prove this,he examines what are the actual data provided by these senses,and shows,or tries to show,that we cannot from them alone construct the world of space and geometry.Hence,if we consider experience impartially and without preconception,we find that it tells us something which is not given by the senses.The senses are not the material of our perceptions,but simply give the occasions upon which our belief is called into activity.The sensation is no more like the reality in which we believe than the pain of a wound is like the edge of the knife.Perception tells us directly and immediately,without the intervention of ideas,that there is,as we all believe,a real external world.
Reid was a vigorous reasoner,and credit has been given to him by some disciples of Kant's doctrine of time and space.Schopenhauer(22)says that Reid's 'excellent work'gives a complete 'negative proof of the Kantian truths';that is to say,that Reid proves satisfactorily that we cannot construct the world out of the sense-given data alone.But,whereas Kant regards the senses as supplying the materials moulded by the perceiving mind,Reid regards them as mere stimuli exciting certain inevitable beliefs.As a result of Reid's method,then,we have 'intuitions.'Reid's essential contention is that a fair examination of experience will reveal certain fundamental beliefs,which cannot be explained as mere manifestations of the sensations,and which,by the very fact that they are inexplicable,must be accepted as an 'inspiration.'(23)Reid professes to discover these beliefs by accurately describing facts.
He finds them there as a chemist finds an element.The 'intuition'is made by substituting for 'ideas'a mysterious and inexplicable connection between the mind and matter.(24)The chasm exists still,but it is somehow bridged by a quasi-miracle.Admitting,therefore,that Reid shows a gap to exist in the theory,his result remains 'negative.'The philosopher will say that it is not enough to assert a principle dogmatically without showing its place in a reasoned system of thought.The psychologist,On the other hand,who takes Reid's own ground,may regard the statement only as a useful challenge to further inquiry.The analysis hitherto given may be insufficient,but where Reid has failed,other inquirers may be more successful.As soon,in fact,as we apply the psychological method,and regard the 'philosophy of mind'as an 'inductive science,'it is perilous,if not absolutely inconsistent,to discover 'intuitions'which will take us beyond experience.The line of defence against empiricism can only be provisional and temporary.In his main results,indeed,Reid had the advantage of being on the side of 'common sense.'Everybody was already convinced that there were sticks and stones,and everybody is prepared to hear that their belief is approved by philosophy.