4. Ibn Khaldûn comes forward with a claim to establish a new philosophical discipline, of which Aristotle had no conception. Philosophy is the science of what exists, developed from its own principles or reasons. But what the Philosophers advance, about the high Spirit-world and the Divine Essence, does not correspond thereto: that which they say on these subjects is incapable of proof. We know our world of men much better; and a more certain deliverance may be given regarding it, by means of observation and inner mental experience. Here facts permit of being authenticated, and their causes discovered. Now, so far as the latter process is feasible in History, i.e. so far as historical events are capable of being traced back to their causes, and historical laws capable of being discovered, History deserves actually to be called Science and a part of Philosophy. Thus the idea of History as Science clearly emerges. It has nothing to do with curiosity, frivolousness, general benefit, edifying effect &c. It should, although in the service of the higher purposes of life, determine nothing except facts, endeavouring to find out their causal nexus. The work must be done in a critical, unprejudiced spirit. The governing principle which rules here is this,—that the cause corresponds to the effect,—that is to say, that like events presuppose the same conditions, or, that under the same circumstances of civilization the like events will occur. Now, as it is a probable assumption that the nature of men and of society undergoes no change by the advance of time, or no considerable change, a living comprehension of the present is the best means of investigating the past. That which is fully known and is under our very eyes permits us to form retrospective conclusions in regard to the less fully known events of an earlier time: it promises even a glance into the future. In every instance, therefore, tradition must be tested by the present; and if it tells us of things which are impossible now, we must for that very reason doubt its truth. Past and Present are as like one another as two drops of water. If understood absolutely, that might have been said even by Ibn Roshd. But according to Ibn Khaldûn it is only quite generally valid as a principle of research. In detail it suffers many a limitation; and in any case it has itself to be established by facts. 5. What then is the subject of History as a philosophical discipline? Ibn Khaldûn answers that it is the Social life,—the collective, material and intellectual culture of Society. History has to show how men work and provide themselves with food, why they contend with each other and associate in larger communities under single leaders, how at last they find in a settled life leisure for the cultivation of the higher arts and sciences, how a finer culture comes into bloom in this way out of rude beginnings, and how again this in time dies away.