Here Buddha found himself at the most difficult problem of Indian speculation, which failed to find an internal transition from not-being to being, from being to not-being, so that in it the principles always remain the same, and cause and effect are equally eternal. Hence in order to be consistent, he must seek the solution of his problem, the cessation of the regenerations, in the annihilation of the cause of these regenerations; and this cause was in his view the intellectual capacity. As the soul is first set free from sensation, and then from the body, so man must finally be set free from the soul, the self, the _Ego_, by destroying the basis and possibility of this; while the adherents of the Sankhya doctrine merely separated the soul from the body, merely looked on at the revolution of the wheel of nature; and the Brahmans would plunge the soul in Brahman. At a later time a great deal of controversy arose as to what Buddha meant by Nirvana, and persons of great eminence in the Buddhist church have had recourse to the explanation that he alone knows what Nirvana is who finds himself in that state. Yet from the process and tendency of Buddha's philosophy, as well as from the most ancient definitions, it is sufficiently clear what condition, what results, were meant to be attained by Nirvana. The most ancient explanations term it, "the cessation of thought, when its causes are suppressed:" they denote it as a condition, "in which nothing remains of that which constitutes existence."[447] With the impossibility of feeling impressions, of knowing anything, and therefore of desiring anything, the being of the individual also ceases, according to Buddha's view, and it was the extinction of this at which he aimed. In Nirvana, according to the older legends, nothing remains but "emptiness;" it is frequently compared with "the exhaustion of a lamp when it goes out."[448] But how this condition is brought about we are not told; we only know that all contact, external or internal, with the world must be removed.[449] When every distinct conception, and even everything that may give rise to such a conception, had been avoided; when a man had put aside every thought, and every excitement of the spirit, he ought to succeed in destroying the thinking principle within him. The man of knowledge has discovered that all which is, is worthless; that nothing exists really and essentially; he has broken through the shells of deception and ignorance. He has diverted and liberated his feeling from these frivolities, and now passes into the condition in which he has nothing more to think of, nothing more to feel, and consequently nothing more to desire; that is, he has attained a state in which feeling and thoughts are extinguished, and continue extinguished. If any feeling or conception remains in this condition, the _Ego_ in Nirvana would feel peace and joy at the thought that nothing any longer existed, that itself ceased to exist. Thus it becomes