The use which Carlyle makes of this doctrine in his interpretation of the religious history of the world and of the crisis in thought of his own day, will be anticipated. All dogmas, forms and ceremonials, he teaches, are but religious vestments--symbols expressing man's deepest sense of the divine mystery of the universe and the hunger and thirst of his soul for God. It is in response to the imperative necessities of his nature that he moulds for himself these outward emblems of his ideas and aspirations. Yet they are only emblems; and since, like all other human things, they partake of the ignorance and weakness of the times in which they were framed, it is inevitable that with the growth of knowledge and the expansion of thought they must presently be outgrown. When this happens, there follows what Carlyle calls the "superannuation of symbols." Men wake to the fact that the creeds and formulas which have come down to them from the past are no longer living for them, no longer what they need for the embodiment of their spiritual life. Two mistakes are now possible, and these are, indeed, commonly made together. On the one hand, men may try to ignore the growth of knowledge and the expansion of thought, and to cling to the outgrown symbols as things having in themselves some mysterious sanctity and power. On the other hand, they may recklessly endeavour to cast aside the reality symbolised along with the discredited symbol itself. Given such a condition of things, and we shall find religion degenerating into formalism and the worship of the dead letter, and, side by side with this, the impatient rejection of all religion, and the spread of a crude and debasing materialism. Religious symbols, then, must be renewed. But their renewal can come only from within. Form, to have any real value, must grow out of life and be fed by it.