Some confusion still exists as to what is implied by this term. Many, for example, having heard that Claude Monet is an Impressionist and observing that he covers his pictures with little dabs of paint, suppose that in this consists Impressionism. Others of wider observation, having found themselves puzzled and even outraged by the vagaries in paint that are committed under cover of Impressionism, have concluded that Impressionism is something which, in the words of the late Lord Dundreary, “No fellah can understand”; no layman, at least; and, according to their temperament, they either foam at the mouth with disgust of Impressionism or regard it as a comparatively harmless form of lunacy. In either case they miss the fact that Impressionism has become a vital principle of modern thought, expressing itself not only in the arts: in painting, sculpture, literature, play-writing, acting, music, and dancing, but also in modern methods of education, and, by a natural extension of the idea involved, even in the modern attitude toward matters of criminology and sanitation. These, however, are modern evolutions from the single, simple principle involved in the Impressionism of Hals and Velasquez. Before discussing this, let us note what is surely interesting and extremely suggestive, namely, that both the rudimentary principle, as it appears in Hals, and the efflorescence to which it attained in the nineteenth century were contemporary with a signal advance in the growth of the scientific spirit. It is, in fact, of the latter that Impressionism is a phase.