Against this reality of the profound "us" which is the genuine spiritual reality, there are innumerable and awe-inspiring difficulties. They are difficulties that so violently oppress our minds and our hearts as to dismay us, and almost force us to give up this concept of a reality on which all other realities depend, and which cannot but be one alone, and infinite, and really universal.[4] Alone, because in it all opposites must coincide: the good and the evil, what is true and what is false, life and death, peace and war, pleasure and pain, yours and mine,--all things, in short, that we have been obliged to sunder and distinguish in order to take our bearings and meet the exigencies of life. Formidable difficulties indeed! And they are the problems of philosophy. It would be childish and senseless to dispose of them by ignoring that concept from which they derive. It is the philosopher's task, it is the strict duty of human thought to face the problems as they rise out of the positions which it has captured in its onward march. For to yield ground, to turn the back to a truth which has been demonstrated to be indispensable, that is impossible. Those who wish to orient themselves in the world to-day must, before all, cling to this: that the basis of every thinkable reality is our spiritual reality, one, infinite, universal,--the reality which unites us all in one sole spiritual life; the reality in which teacher and pupils meet when by their reciprocal comprehensions they constitute a real school.