Parmenides asserted that Being is globe-shaped, and therefore finite. Now it was an essential part of the doctrine of Parmenides that empty space is non-existent. Empty space is an existent non-existence. This is self-contradictory, and for Parmenides, therefore, empty space is simply not-being. There are, for example, no interstices, or empty spaces between the particles of matter. Being is "the full," that is, full space with no mixture of empty space in it. Now Melissus agreed with Parmenides that there is no such thing as empty space; and he pointed out, that if Being is globe-shaped, it must be bounded on the outside by empty space. And as this is impossible, it cannot be true that Being is globe-shaped, or finite, but must, on the contrary, extend illimitably through space. This makes it quite clear that Parmenides, Melissus, and the Eleatics generally, did regard Being as, in some sense, material. [Footnote 5: _Early Greek Philosophy_, chap. iv. § 89.] Now, however, let us turn to the other side of the picture. What ground is there for regarding Parmenides as an idealist? In the first place, we may say that his ultimate principle, Being, whatever he may have thought of it, is not in fact material, but is essentially an abstract thought, a concept. Being is not here, it is not there. It is not in any place or time. It is not to be found by the senses. It is to be found only in reason. {48} We form the idea of Being by the process of abstraction. For example, we see this desk. Our entire knowledge of the desk consists in our knowledge of its qualities. It is square, brown, hard, odourless, etc. Now suppose we successively strip off these qualities in thought--its colour, its size, its shape. We shall ultimately be left with nothing at all except its mere being. We can no longer say of it that it is hard, square, etc. We can only say "it is." As Parmenides said, Being is not divisible, movable; it is not here nor there, then nor now. It simply "is." This is the Eleatic notion of Being, and it is a pure concept. It may be compared to such an idea as "whiteness." We cannot see "whiteness." We see white things, but not "whiteness" itself. What, then, is "whiteness"? It is a concept, that is to say, not a particular thing, but a general idea, which we form by abstraction, by considering the quality which all white things have in common, and neglecting the qualities in which they differ. Just so, if we consider the common character of all objects in the universe, and neglect their differences, we shall find that what they all have in common is simply "being." Being then is a general idea, or concept. It is a thought, and not a thing. Parmenides, therefore, actually placed the absolute reality of things in an idea, in a thought, though he may have conceived it in a material and sensuous way. Now the cardinal thesis of idealism is precisely this, that the absolute reality, of which the world is a manifestation, consists in thought, in concepts.