Before embarking on the answer to this question, it must be noted that the answer provided below is based on the school of Transcendent Theosophy, i.e., Sadrian philosophy. In this light, the answer will be expounded under two main headings and several subtopics.
Under the first heading, “The Existence of Spirit in Animals”, the following topics will be examined:
1. In all philosophical discussions pertaining to the question of the spirit, animal spirit is always enumerated as an indubitable instance of spirit. However, obviously the various forms of spirit possess their own peculiarities which distinguish them from one another.
2. What comprises the essence of an animal is its animal spirit, and to imagine the animal without an animal spirit would be to downgrade it to the lower degree of existence—i.e., vegetable existence.
3. In several animals, such as the honey bee, the spider, etc., the signs of an indwelling spirit are clearly noticeable.
4. Scholars provide various sorts of evidence for the existence of animal spirit—among them: the presential knowledge of animals of their own essences, the role that will plays in animal behaviour, the resurrection of animal spirits in the Hereafter.
5. The fact that animals can comprehend imaginal and immaterial forms and the performance by them of varying dissimilar actions.
The topics covered in the second heading, “The Difference between the Animal and the Human Spirit”, are as follows:
1. Human nature is different from animal nature. The material components of the human body are relatively finer and more perfect.
2. Human spirit also differs from animal spirit in many respects; including the human capacity to communicate by employing letters, words, thoughts, etc., and the human psychological variations—such as laughter, weeping, etc.—in response to different external phenomena.
3. The existence of art, industry, and human innovation display clearly the superiority of the human soul as they have no place in the realm of animals.
4. The essential difference of the human soul from the animal soul is that the former is intellectual while the latter is imaginal.
5. In addition, the sole pursuit of the animal soul is the gratification of the corporeal needs while the scope of human soul, in terms of its conceptual and practical aspects, stretches to the farthest reaches of existence.
This question will be considered in the light of Sadrian philosophy, i.e., Transcendent Theosophy. In the numerous works by Mulla Sadra and the subsequent philosophers who espoused his philosophy, there are numerous allusions and in some cases detailed expositions of the question in hand in the chapters dealing with the topics of soul, Resurrection, knowledge, and comprehension. The material prepared for this question will be presented under two main headings and five shorter sections. The essay will then end with the topic of the difference between the human soul and the animal soul.
The Existence of Spirit in Animals
The Animal Soul as One of the Instances of Spirit in Existence
In philosophical inquiries into the topic of the soul, where the soul is defined, it is commonly divided into three classes: vegetable soul, animal soul, and human soul. Despite the fact that each one of these classes possesses its own peculiarities which distinguish it from its counterparts, they all share a common reality and essence. The soul is a spiritual and immaterial existent which incorporates spiritual faculties, whether it be the intellectual soul, the imaginal soul, or the vegetable soul.
The Creation of the Animal Spirit as One of the Phases of the Origination of the Realm of Materiality
Mulla Sadra is among those thinkers who hold that the origination of material existents was carried out in stages, starting from the simplest and advancing to the stage of the most perfect elements. In some of these stages, the mere combination of material ingredients was not enough and thus the addition of an immaterial element to the composition was called for, so as to satisfy the requirements of that particular order of creation. One such stage was the creation of the animal. The spirit that was infused in the composition to bring about the animal existence is termed the “animal spirit”.
Hence, not only does the animal possess a soul, furthermore it owes its essence to that soul. The addition of the soul to the material ingredients is a requirement of the order of the realm of materiality. And the same case applies to the realms of the human being and the vegetable. The immaterial spirit or soul is what distinguishes some material entities from others. In the inanimate, the lack of such a spirit is what makes their nature, while in others the possession thereof makes them what they are. And among the animate, it is the variation in the degrees of the spirit that sets them apart in differing levels of existence. The vegetable soul lies at the bottom while the human spirit enjoys the apex and the animal spirit the median seat.
The Outward Manifestations of the Soul in the Animal
The appearance of certain traits in various animals—such as the building of the hexagonal hive by the honeybee, the weaving of the delicate web by the spider, the monkey’s and the parrot’s mimicking the human being, the cleverness of the horse, the authority of the lion, the faithfulness of the dog, the deceptiveness of the crow, etc.—are, in the view of Mulla Sadra, evidence of the existence of a limited intelligence which indicates the presence of a soul in the animal. The character traits of some of these animals are so complex as to render them very close to the level of the human being.
Scientific Indications Corroborating the Existence of an Animal Spirit
All animals possess an imaginal soul that is similar to the human imaginal soul. The animal spirit is at the level of imaginal immateriality, which is the intermediate level between the realm of the sensible and the realm of Intellection. The zenith of animal existence is the imaginal existence, hence accommodating the imaginal soul. It is due to this degree of immateriality and spiritual potency that it possesses presential self-knowledge, for no inanimate object can ever have self-knowledge.
According to Mulla Sadra, all actions in the cosmos derive from will. This is so even in the case of the vegetable and the inanimate, with the difference that in their case the will in question is that of the higher intellects and spirits. That is, the inanimate and the vegetable are involuntarily the means of the realization of the higher wills. But in the case of the animal and the human being, the prerequisites for the actualization of an action that falls in the scope of their volition must be realized by themselves, and it is for this reason that the actions of animals and human beings are unpredictable while those attributed to the inanimate and the vegetable are monotonous. The source where animal action originates is the imaginal and the conjectural faculty while in the human being it is the practical intellect. Imagination, speculation, intellection, will, etc., are all manifestations of a soul and as such are the traits that distinguish the creature possessed of a spirit from that which lacks it.
In addition to the worldly effects of the soul, one can also point to the issues of eschatology and the Resurrection of the body and soul of all animate creatures possessed of a soul. For this reason, all the philosophers who have dealt with the question of eschatology have designated a part to the subject of the resurrection of animal souls, its conditions, and other relevant details.
Proofs for the Existence of Spirit in the Animal
The animal is undoubtedly endowed with a spirit, i.e., an immaterial aspect, for it possesses the imaginal faculty which is capable of comprehending ghosts and imaginal forms. These things are not sensorially tangible and hence are not inhabitants of the material world. Therefore, the imaginal faculty, which is the receptacle for the comprehension of these immaterial existents, is also not sensorially tangible and as such is not corporeal. For, every material existent occupies a certain material location. This also holds true of the dependents of that material existent. This is while the imaginal forms and ghosts comprehended by the imaginal faculty do not occupy a certain material location, and so it follows that the imaginal faculty, which is the receptacle for their impressions, also lacks material location and hence is not corporeal.
Moreover, the variety of the actions performed by the animals does not only corroborate the existence of a soul in them but can also stand as a cogent argument for substantiating this claim. For the effects derived from material existents and inanimate objects are immutably monotonous and repetitious. Thus, when the state of an existent is so unpredictable as to make it difficult to even catch two identical actions from the same agent due to it altering its reactions based on varying external and internal circumstances—in such a case, reason rules that there must be some other immaterial factor involved.
The Difference between the Animal Soul and the Human Soul
It was pointed out that from the perspective of philosophy, the existentiation of the material realm was a progressive process carried out in various stages, each more complex than the preceding stage. In this light, although the material constitution of the animal was a finer composition in comparison to that of the vegetable, which qualified it for receiving the animal soul, yet it still needed to be perfected further in order to accommodate the human spirit so as to bring about the human being, the being which had been selected as the dominant creature capable of utilizing all other creatures in his service, as he was the goal and end of creation.
Although the human being in a strictly logical categorization is from the same material as that which constitutes the animal, the thing that makes it unique is so profound that if, by way of analogy, all the rest of the animals were set on one side of a scale and the human being on the opposite, he would definitely weigh heavier. The human being is capable of speech and as such is able to communicate his thoughts and intentions with fellow human beings in the form of letters and words, which can be formed into innumerable permutations and combinations. But the capacity of animals like the parrot in manipulating words is limited and confined to mimicking and is devoid of any thought. Also the communication of certain animals in the form of sounds and signals—like the honey bee, the ant, etc.—which has been scientifically observed, is a fixed method not capable of change during the course of their lives. But in the case of the human being, although initially learning many of his language skills by way of imitation, eventually every individual comes to possess a distinct method of communication.
The psychological impressions that the human being receives from the environment and the physiological and psychological states that result thereof—such as amazement and laughter in response to rare but pleasing events, grief and weeping in response to adverse circumstances, shamefulness following unbecoming conduct, and anxiety and hope vis-à-vis the past, the present, and the future—and the planning and decisions that the human being makes based on these states are unique qualities. And although the ant’s performance in storing food can be considered as a sort of forethought, it is nevertheless an instinctual and involuntary behaviour, for it is always done in the same manner and in the same timeframe. This is in contrast to the human being whose seemingly passive psychological states—such as laughter, weeping, etc.—are absolutely voluntary and thus are manageable in special circumstances and through prudence.
Craftsmanship, art, industry, innovation, and, in the words of Mulla Sadra, “the amazing practical innovations” that have flourished in the course of human history, and the fact that man has single-handedly changed the face of the world and has either manipulated all the elements of this world or is on the verge thereof is proof of the inimitable spiritual superiority of the human being, for not even a slight fraction of this sort of activity has appeared in the animal realm. The entire lifespan of an animal is occupied merely by roaming about in pursuit of the dictates of its imaginal and conjectural faculties.
The animal’s imaginal and conjectural planning revolve around its personal or specific benefit. In keeping itself safe from various dangers and securing water and food and satisfying its sexual appetite, it is, on the one hand, safeguarding its individual interests and, on the other hand, contributing to the survival of its species. It is for this reason that the animal soul is referred to as “the imaginal soul”. The summit of the imaginal soul is the beginning point for the human soul. The animal can advance only up to the point where the human domain begins. In other words the final reaches of the realm of the imaginal soul is just the beginning of the domain of the intellect; it is the threshold through which one enters into the human realm, to which there is no conceivable end. It is the intellect that defines the human being. Hence, those who do not take advantage of their intellects remain at the level of the beast.
Through the theoretical intellect, the human being is able to comprehend immaterial concepts and thereby to transform his ignorance to knowledge. The human being draws a mental image of all that he encounters by the senses. It then uses these concepts to form another set of concepts which are more universal and abstract. The latter concepts enhance the mind’s innovative capabilities. The human mind uses the latter concepts to arrive at various sorts of rules, judgments, and arguments and by juxtaposing them in a systematized fashion produces systematic thought, philosophy, and the sciences. If the human being persists in this endeavour, every new day will expand the horizon of his cognition until he passes from the human domain—which is the admixture of body and soul, of corporeal needs and intellectual faculties—to the domain of pure intellection, where he is united with the Madonna Intelligenza at which stage he finds the whole world realized within the scope of his knowledge.
The genuine human being makes his practical intellect—which derives its directives from the knowledge acquired by the theoretical intellect—the guide of his conduct. The theoretical and practical intellects have limitless power in both the material and the spiritual directions. The human being has succeeded in obtaining knowledge previously not even imaginable, thereby reshaping his surrounding world. The innermost reality of the world is just as much accessible to him, this being demonstrated by those who have attained to human perfection. By the light of their esoteric knowledge—which can best be referred to as ‘irfan—they have traversed the path to Divine proximity. That is, they have conquered the visible realm, the Realm of Intellection, the Supreme Dominion, and the Domain of Invincibility, thereby ascending to the zenith of human perfection.
The interesting point is that these two paths of infinite possibilities, i.e., the paths of exoteric and esoteric knowledge, are in no way at odds. To the contrary, the more one studies the worldly phenomena, given that he be fair and unbiased, the better he acknowledges the profundity of this world and the greatness of its creator. Likewise, he who has traversed the path of ‘Irfan understands all the more acutely the necessity of studying the worldly phenomena so as to better admire the majesty of the Creator.
 This term will be explained further in the text.