The Philosophy of Reflection Volume 2 of 3 - Bog

First, then, as to the ultimate and universal ele ments of phenomena. These are three in number, the element of Feeling, which we have called the material element; the element of Time or duration; and the element of Space, which primarily attaches only to the two kinds of feeling known as sight and touch, including or combined with sense of effort in muscle or nerve. The two latter elements, those of Time and Space, are called the formal elements.