All human knowledge begins from sensations which are gradually transformed into perceptions. The earlier stages of intellection are completely conditioned by the presence of external reality. But the progress of knowledge means to be able to think without being conditioned by matter. Thought begins with matter, but its object is to gradually free itself from the primary condition of its own possibility. A higher stage, therefore, is reached in imagination--the power to reproduce and retain in the mind the copy or image of a thing without reference to the external objectivity of the thing itself. In the formation of concepts thought reaches a still higher stage in point of freedom from materiality; though the concept, in so far as it is the result of comparison and assimilation of percepts, cannot be regarded as having completely freed itself from the gross cause of sensations. But the fact that conception is based on perception, should not lead us to ignore the great difference between the nature of the concept and the percept. The individual (percept) is undergoing constant change which affects the character of the knowledge founded on mere perception. The knowledge of individuals, therefore, lacks the element of permanence. The universal (concept), on the other hand, is not affected by the law of change. Individuals change; the universal remains intact. It is the essence of matter to submit to the law of change: the freer a thing is from matter, the less liable it is to change. God, therefore, being absolutely free from matter, is absolutely changeless; and it is His complete freedom from materiality that makes our conception of Him difficult or impossible. The object of all philosophical training is to develop the power of "ideation" or contemplation on pure concepts, in order that constant practice might make possible the conception of the absolutely immaterial. 3. _How the one creates the many._ In this connection it is necessary, for the sake of clearness, to divide Ibn Maskawaih's investigations into two parts:--