According to a famous philosophical view...

According to a famous philosophical view, the criteria of unity being in every natural or living existent is an abstract decree (which is the equivalent to it being not compound) and imperceptive by the name of ‘nature’ or (genus) ‘form’ and does not change due to the transformation or replacement of matter. The natural factor in these living existents, which is comprised of different actions such as growth, digestion, reproduction, etc is called the soul (nafs).

Previous philosophers have regarded the mineral and animal soul as materialistic and the human soul as immaterial. Many of the Islamic philosophers such as Sadruddin Shirazi regarded the animal soul as having different levels of immateriality and recognized perceptiveness, and will (irādah) as the signs of immaterial existents.

However the previous and present materialistic philosophers (positivist) have limited the existent to matter and denied the immateriality of the spirit and the latter have completely denied the basis of anything imperceptible. The positivists do not accept the ‘form’ (genus) or nature of any existent as it is immaterial and will not produce a correct answer for representing the criteria of unity in the living existent.

On the basis that it is the unity in minerals, which is the soul of the mineral, the mineral kingdom is categorized by a special form or soul, which is substantially susceptible and when this potentiality or susceptibility is destroyed, the soul and the form of it is also destroyed.

But, if the same substance accepts life or a new form, then a new mineral soul is allotted to it and a new plant after the old one has been destroyed (even if perfect in resemblance) will not be considered as the same old plant. However for the animal and human soul, the soul is immaterial and can remain even after the body has been completely destroyed. Likewise, the new replaced or transformed cells preserve the unity in a person, and s/he is known as that very previous and same individual.

Even before death the unity of the spirit in a particular body is the criteria of the unity. Those who regard the existence (wujūd) of humans and animals as being limited to this material realm and their spirit as being imperceptible and as a component of their physical body and thus destroyed along with the material destruction of the body, will not grasp the correct understanding of Resurrection.