The word "progressive," however, raises one of the most complex issues in sociology. It would be needless to point out, were it not well to anticipate objection, that the foregoing summaries are not offered as a complete theory of progress even as commonly conceived, much less as sufficing to dismiss the dispute[134] as to what progress is, or what basis there is for the modern conceptions bound up with the word. Our generalisations proceed on the assumption--not of course that human affairs must constantly improve in virtue of some cosmic law, but--that by most men of any education a certain advance in range of knowledge, of reflection, of skill, of civic amenity, of general comfort, is held to be attainable and desirable; that such advances have clearly taken place in former periods; and that the due study of these periods and of present conditions may lead to a further and indefinitely prolonged advance. Conceiving progress broadly as occurring by way of rise in the quantity and the quality of pleasurable and intelligent life, we beg the question, for the purposes of this inquiry, as against those who may regard such a tendency with aversion, and those who may deny that such increase ever takes place. Taking as proved the evolution of mankind from lower forms of animal life, we conceive such evolution as immeasurably slow in the period before the attainment of agriculture, which may serve as the stage at which what we term "civilisation" begins. Only with agriculture begins the "civitas," as distinct from the horde or tribe. Thenceforth all advance in arts and ethics, no less than in political co-ordination, counts as "civilisation." The problem is, how to diagnose advance. All of us, roughly speaking, understand by progress the moving of things in the way we want them to go; and the ideals underlying the present treatise are easily seen, though it does not aim at an exhaustive survey of the conditions and causes of what it assumes to be progressive forms or phases of civilisation. To reach even a working theory, however, we have to make, as it were, cross-sections in our anatomy, and to view the movement of civilisation in terms of the conditions which increase men's stock of knowledge and extend their imaginative art. To lay a foundation, we have to subsume Buckle's all-important generalisation as to the effect of food and life conditions in differentiating what we may broadly term the primary from the secondary civilisation. Thus we think from "civilisation" to _a_ civilisation.