Now let us consider what of worth there is in this Eleatic principle, and what its defects are. In the first place, it is necessary for us to understand that the Eleatic philosophy is the first monism. A monistic philosophy {63} is a philosophy which attempts to explain the entire universe from one single principle. The opposite of monism is therefore pluralism, which is that kind of philosophy which seeks to explain the universe from many ultimate and equally underived principles. But more particularly and more frequently we speak of the opposite of monism as being dualism, that is to say, the position that there are two ultimate principles of explanation. If, for example, we say that all the good in the universe arises from one source which is good, and that all the evil arises from another source which is evil, and that these sources of good and evil cannot be subordinated one to the other, and that one does not arise out of the other, but both are co-ordinate and equally primeval and independent, that position would be a dualism. All philosophy, which is worthy of the name, seeks, in some sense, a monistic explanation of the universe, and when we find that a system of philosophy breaks down and fails, then we may nearly always be sure its defect will reveal itself as an unreconciled dualism. Such a philosophy will begin with a monistic principle, and will attempt to derive or deduce the entire universe from it, but somewhere or other it comes across something in the world which it cannot bring under that principle. Then it is left with two equally ultimate existences, neither of which can be derived from the other. Thus it breaks out into dualism.