The dualist may maintain that we have a direct knowledge of matter and of mind, and he may content himself with such a statement, doing little to make clear what we mean by matter and by mind.  In this case, his position is little different from that of the plain man who does not attempt to philosophize.  Thomas Reid (section 50) belongs to this class.

On the other hand, the dualist may attempt to make clear, through philosophical reflection, what we mean by the matter and mind which experience seems to give us.  He may conclude:—­

(1) That he must hold, as did Sir William Hamilton, that we perceive directly only physical and mental phenomena, but are justified in inferring that, since the phenomena are different, there must be two kinds of underlying substances to which the phenomena are referred.  Thus, he may distinguish between the two substances and their manifestations, as some monists distinguish between the one substance and its manifestations.

(2) Or he may conclude that it is futile to search for substances or realities of any sort behind phenomena, arguing that such realities are never revealed in experience, and that no sound reason for their assumption can be adduced.  In this case, he may try to make plain what mind and matter are, by simply analyzing our experiences of mind and matter and coming to a clearer comprehension of their nature.

As the reader has probably remarked, the philosophy presented in the earlier chapters of this book (Chapters III to XI) is dualistic as well as realistic.  That is to say, it refuses to rub out the distinction between physical phenomena and mental phenomena, either by dissolving the material world into ideas; by calling ideas secretions or functions of the brain; or by declaring them one in a fictitious entity behind the veil and not supposed to be exactly identical with either.  And as it teaches that the only reality that it means anything to talk about must be found in experience, it is a dualism of the type described in the paragraph which immediately precedes.

Such a philosophy does not seem to do violence to the common experience of minds and of physical things shared by us all, whether we are philosophers or are not.  It only tries to make clear what we all know dimly and vaguely.  This is, I think, a point in its favor.  However, men of great ability and of much learning have inclined to doctrines very different; and we have no right to make up our minds on such a subject as this without trying to give them an attentive and an impartial hearing.

59.  SINGULARISM AND PLURALISM.—­There are those who apply to the various forms of monism the title Singularism, and who contrast with this Pluralism, a word which is meant to cover the various doctrines which maintain that there is more than one ultimate principle or being in the universe.

It is argued that we should have some word under which we may bring such a doctrine, for example, as that of the Greek philosopher Empedocles (born about 490 B.C.).  This thinker made earth, water, fire, and air the four material principles or “roots” of things.  He was not a monist, and we can certainly not call him a dualist.