They differ among themselves because of the sources (l) of their clay (from which they have been created). This is because they are either from saltish soil or sweet soil or from rugged earth or soft earth. They, resemble each other on the basis of the affinity of their soil and differ according to its difference. Therefore, sometimes a person of handsome features is weak in intelligence, a tall statured person is of low courage, a virtuous person is ugly in appearance, a short statured person is far-sighted, a good-natured person has an evil trait, a person of perplexed heart has bewildering mind and a sharp-tongued person has a wakeful heart.
(l). Amir al-mu'minin has ascribed the differences in features and characters of people to the differences in the clay from which they are created and according to which their features are shaped and the skeletons of their characters are formed. Therefore, to the extent that their clay of origin is akin, their mental and imaginative tendencies too will be similar and to the extent by which they differ, there will be a difference in their inclinations and tendencies. By origins of a thing are meant those things on which its coming into existence depends, but they should not be its cause. 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 Nahj al-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.
In any case, whether the original factors are the cause of differences in features and conduct or the elementary constituents are the cause, these words appear to lead to the negation of volition and to prove the compulsion (of destiny) in human actions, because if man's capacity for thinking and acting is dependent on "tinah" then he would be compelled to behave himself in a fixed way on account of which he would neither deserve praise for good acts nor be held blame worthy for bad habits. But this hypothesis is incorrect because it is well established that just as Allah knows everything in creation after its coming into being, in the same way He knew it before its creation. Thus, He knew what actions man would perform of his free will and what he would leave. Therefore, Allah gave him capacity to act according to his free will, and created him from a suitable "tinah". This tinah is not the cause of his actions so as to snatch away from him his free will but the meaning of creating from suitable tinah is that Allah does not by force stand in man's way but allows him to tread the path he wants to tread of his own free will.