It is evident that many colours are hampered and even nullified in effect by many forms. On the whole, keen colours are well suited by sharp forms (e.g., a yellow triangle), and soft, deep colours by round forms (e.g., a blue circle). But it must be remembered that an unsuitable combination of form and colour is not necessarily discordant, but may, with manipulation, show the way to fresh possibilities of harmony. Since colours and forms are well-nigh innumerable, their combination and their influences are likewise unending. The material is inexhaustible. Form, in the narrow sense, is nothing but the separating line between surfaces of colour. That is its outer meaning. But it has also an inner meaning, of varying intensity, [Footnote: It is never literally true that any form is meaningless and "says nothing." Every form in the world says something. But its message often fails to reach us, and even if it does, full understanding is often withheld from us.] and, properly speaking, FORM IS THE OUTWARD EXPRESSION OF THIS INNER MEANING. To use once more the metaphor of the piano--the artist is the hand which, by playing on this or that key (i.e., form), affects the human soul in this or that way. SO IT IS EVIDENT THAT FORM-HARMONY MUST REST ONLY ON A CORRESPONDING VIBRATION OF THE HUMAN SOUL; AND THIS IS A SECOND GUIDING PRINCIPLE OF THE INNER NEED. The two aspects of form just mentioned define its two aims. The task of limiting surfaces (the outer aspect) is well performed if the inner meaning is fully expressed. [Footnote: The phrase "full expression" must be clearly understood. Form often is most expressive when least coherent. It is often most expressive when outwardly most imperfect, perhaps only a stroke, a mere hint of outer meaning.] The outer task may assume many different shapes; but it will never fail in one of two purposes: (1) Either form aims at so limiting surfaces as to fashion of them some material object; (2) Or form remains abstract, describing only a non-material, spiritual entity. Such non-material entities, with life and value as such, are a circle, a triangle, a rhombus, a trapeze, etc., many of them so complicated as to have no mathematical denomination. Between these two extremes lie the innumerable forms in which both elements exist; with a preponderance either of the abstract or the material. These intermediate forms are, at present, the store on which the artist has to draw. Purely abstract forms are beyond the reach of the artist at present; they are too indefinite for him. To limit himself to the purely indefinite would be to rob himself of possibilities, to exclude the human element and therefore to weaken his power of expression.