Then as to their ideas about immortality. If immortality is a necessary phenomenon due to the intellectual nature of the soul and dependent upon the degree of intellectual knowledge it possesses, how much knowledge must a man have to be immortal? If any amount is sufficient, then every rational soul is immortal, for everybody knows at least the axioms of logic and mathematics, such as that things equal to the same thing are equal to each other, that a thing cannot both be and not be, and so on. If a knowledge of the ten categories is necessary, and of the other universal principles which embrace existence conceptually, though not practically, this knowledge can be gotten in a day, and it is not likely that a man can become an angel in a day. If on the other hand one must know everything not merely conceptually but in detail, no one can ever acquire universal knowledge and no one is immortal The philosophers may be excused because this is the best they can do with the help of pure reason. We may commend them for their mode of life in accordance with the moral law and in freedom from the world, since they were not bound to accept our traditions. But it is different with us. Why should we seek peculiar proofs and explanations for the immortality of the soul, since we have promises to that effect whether the soul be corporeal or spiritual? If we depend upon logical proof, our life will pass away without our coming to any conclusion.[209] Judah Halevi takes issue also with the Mutakallimun. These, as we know, were Mohammedan theologians who, unlike the philosophers, were not indifferent to religion. On the contrary their sole motive in philosophizing was to prove the dogmas of their faith. They had no interest in pure speculation as such. Judah Halevi has no more sympathy with them than with the philosophers. Owing to the fact that the Karaites were implicit followers of the Kalam and for other reasons, no doubt, more objective, he thinks less of them than he does of the philosophers. The only possible use, he tells us, of their methods is to afford exercise in dialectics so as to be able to answer the arguments of unbelievers. To the superficial observer the Mutakallim may seem to be superior to the prophet, because he argues, whereas the latter affirms without proving. In reality, however, this is not so. The aim of the Mutakallim is to acquire the belief which the prophet has by nature. But his Kalam may injure his belief instead of confirming it, by reason of the many difficulties and doubts it introduces. The prophet, who has natural belief, teaches not by means of dialectic discussion. If one has a spark of the true belief in his nature, the prophet by his personality will benefit him by a slight hint. Only he who has nothing of true belief in his nature must have recourse to Kalam, which may benefit him or injure.