Number.
The figure 1 is characteristic of unity and measure. The figure 2, which is the measure in the 1, should become subordinate in its greatness and be equal with it. It is another one which gives birth to the idea of number.
The idea of number can only arise from the presence of terms of the same nature. Thus the idea of number cannot arise from the presence of a cart and a toad. We shall thus have two very distinct unities, having no kind of relation to each other. There must, therefore, be equality before there can be number. This is so true that we cannot say of a man and a child that they are two men or two children, because the one is not equal to the other. It is, therefore, from the point of an attributive equality that we are enabled to say: They are two. But we can say: There are two beings, because in regard to being they are equal one to the other. We now understand how two equals one, that the two figures have an equal importance, and that the figure 1 contains exclusively the idea of measure; the figure 2 contains the idea of number, which is not in the 1, this being the characteristic feature by which the two terms differ.
Now, how are we to form a perfect unity between these two equal but distinct terms?
A single operation will suffice to give us the idea we wish, and this operation is revealed to us entire in the word weight. In fact, the two terms can only be united by this word. We feel that 1 and 2 give us a common weight, the sum of which is represented by the figure 3. The figure 3 is, therefore, equal in importance to 1 and to 2; it maintains equality in the terms of which it is the representative, and its characteristic feature is equally important with those already described.
Thus to the figure 1 belongs the idea of measure; to the figure 2 belongs the idea of number; to the figure 3 belongs exclusively the idea of reünion, of community, of unity in fine, which no other figure can reveal to us. We may say: 1 and 1 are equal among themselves, in the unity of the figure 3; or, in other words: Measure and number find their unity in weight.