Distinct and often in conflict, these two orders of knowledge are none the less _solidaire_; they are always developed by their action the one upon the other, and tend to a higher unity, the need for which gives rise to attempts, renewed from age to age, at a metaphysical synthesis. If you take the disciplines as taught in the schools to-day, you will find that they are almost all mixed sciences such as history, social economy, politics, philosophy, etc. So soon as the savant rises above the simple description of phenomena, and wishes to organise his cosmos by formulating the unity and harmony of it, he necessarily borrows this principle of organisation and of harmony from the experience of his subjective life. On the contrary, religion, art, morality, can only be realised in the conditions prescribed to them by science properly so called, and the last problem always propounded to human thought at each stage of its development is the conciliation of the _moral idea_ acquired by the exercise of the will, and the _scientific idea_ furnished by its experience of the world. There is no question, then, of separating the two orders of knowledge, but of referring each of them to its true source, and preventing a confusion which, mixing everything up, renders everything uncertain. It is impossible in good psychology to trace to one centre the divergent manifestations of our spiritual life, and to drive the moral into the physical or the physical into the moral. Our spiritual life is like an ellipse with two centres of light: on the one side, the centre of _receptive life_, where all the sensations received are elaborated into phenomenal knowledge; on the other, the centre of _active life_, at which are concentrated all the revelations of the mind's own inner energy. The line of the ellipse described by the relation and the distance of these two centres is the approximate but never perfect synthesis of the two kinds of data which thus arrive in consciousness. He who does not distinguish these two centres, and transforms the ellipse into a circumference with equal rays and an unique centre, necessarily remains in chaos and old night. From these general considerations is naturally deduced the specific character of religious knowledge, its inward nature and its range. 4. _The Subjectivity of Religious Knowledge_ The first contrast that we have seen to arise between the knowledge of Nature and religious knowledge is that the first is _objective_, and that the second can never pass out of _subjectivity_. This does not mean that the second is less certain, but that it is of another order, and is produced in another way and with other characteristics.