From our tenet that the cause and effect are identical, it follows that the effect does not exist distinct from the cause; thus the cloth is not something distinct from the threads, as it abides in the latter [as its material cause]; but where this identity is not found, there we do not find the relation of cause and effect; thus a horse and a cow are distinct from each other [for one is not produced from the other, and therefore their qualities are not the same]; but the cloth is an acknowledged effect, and therefore not anything different from its cause.[357] If you object that, if this were true, the separate threads ought to fulfil the office of clothing, we reply, that the office of clothing is fulfilled by the threads manifesting the nature of cloth when they are placed in a particular arrangement. As the limbs of a tortoise when they retire within its shell are concealed, and, when they come forth, are revealed, so the particular effects, as cloth, &c., of a cause, as threads, &c., when they come forth and are revealed, are said to be produced; and when they retire and are concealed, they are said to be destroyed; but there is no such thing as the production of the non-existent or the destruction of the existent. As has been said in the Bhagavad Gítá (ii. 16)-- "There is no existence for the non-existent, nor non-existence for the existent." And, in fact, it is by inference from its effects that we establish the existence of the great evolvent, Nature (_prakṛiti_). This has been said [in the Káriká, § 9]-- "Effect exists, for what exists not can by no operation of cause be brought into existence; materials, too, are selected which are fit for the purpose; everything is not by every means possible; what is capable does that to which it is competent; and like is produced from like."[358]