The word "tin" is the plural of "tinah" which means origin or basis.

The word "tin" is the plural of "tinah" which means origin or basis. Here "tinah" means semen which after passing through various stages of development emerges in the human shape. Its origin means those constituents from which those items are created which help in the formation of semen. Thus, by saltish, sweet, soft or hard soil the reference is to these elementary constituents.

Since those elementary constituents carry different properties the semen growing out of them will also bear different characteristics and propensities which will (eventually) show forth in the differences in features and conduct of those borne in it. Ibn Abi'l-Hadid has written (in Sharh Nahjul Balaghah, vol. 13, p. 19) that "origins of tinah" implies those preservative factors which are different in their properties as Plato and other philosophers have held.

The reason for calling them "origins of tinah" is that they serve as an asylum for the human body and prevent the elements from diffusion. Just as the existence of a thing hinges on its basis, in the same way the existence of this body which is made up of elements depends on preservative factors. So long as the preservative factor exists the body is also safe from disruption and disintegration and the elements too are immune to diffusion and dispersal.

When it leaves the body the elements also get dispersed. According to this explanation Amir al-mu'minin's words would mean that Allah has created different original factors among whom some are vicious and some are virtuous, some are weak and some are strong, and every person will act according to his original factor.

If there is similarity in the inclinations of two persons it is because their original factor are similar, and if their tendencies differ it is because their original factors do not have any similarity. But this conclusion is not correct because Amir al-mu'minin's words do not only refer to differences in conduct and behaviour but also of features and shape and the differences of features and shape cannot be the result of differences in original factors.