He who dispenses with doctors is prone to abandon himself to charlatans. Thus it has befallen those who have believed in the natural laws of the beautiful. Artists sometimes adopt empirical canons, such as that of the proportions of the human body, or of the golden section, that is to say, of a line divided into two parts in such a manner that the less is to the greater as is the greater to the whole line (_bc: ac=ac: ab_). Such canons easily become their superstitions, and they attribute to such the success of their works. Thus Michael Angelo left as a precept to his disciple Marco del Pino of Siena that "he should always make a pyramidal serpentine figure multiplied by one, two, three," a precept which did not enable Marco di Siena to emerge from that mediocrity which we can yet observe in his many works, here in Naples. Others extracted from the sayings of Michael Angelo the precept that serpentine undulating lines were the true _lines of beauty_. Whole volumes have been composed on these laws of beauty, on the golden section and on the undulating and serpentine lines. These should in our opinion be looked upon as the _astrology of Aesthetic_. XV THE ACTIVITY OF EXTERNALIZATION, TECHNIQUE AND THE THEORY OF THE ARTS [Sidenote] _The practical activity of externalization._ The fact of the production of the physically beautiful implies, as has already been remarked, a vigilant will, which persists in not allowing certain visions, intuitions, or representations, to be lost. Such a will must be able to act with the utmost rapidity, and as it were instinctively, and also be capable of long and laborious deliberations. Thus and only thus does the practical activity enter into relations with the aesthetic, that is to say, in effecting the production of physical objects, which are aids to memory. Here it is not merely a concomitant, but really a distinct moment of the aesthetic activity. We cannot will or not will our aesthetic vision: we can, however, will or not will to externalize it, or better, to preserve and communicate, or not, to others, the externalization produced. [Sidenote] _The technique of externalization._ This volitional fact of externalization is preceded by a complex of various kinds of knowledge. These are known as _techniques_, like all knowledge which precedes the practical activity. Thus we talk of an artistic technique in the same metaphorical and elliptic manner that we talk of the physically beautiful, that is to say (in more precise language), _knowledge employed by the practical activity engaged in producing stimuli to aesthetic reproduction_. In place of employing so lengthy a phrase, we shall here avail ourselves of the vulgar terminology, since we are henceforward aware of its true meaning.