In St. Thomas Aquinas’ comprehensive Summa Theologica, the work consists of a detailed summary that pertains to the theological explanation on the notion of the existence of God and the relationship between God and man. The summa also tackles the divine reconciliation of man and how it is achieved through Christ. Aquinas also enumerates the nature of God and proofs of his existence through questions supported by arguments and claims. This method adopts several Aristotelian concepts where Aquinas explains the nature, origin, and purpose of the universe and how the totality of all concepts in a universal existence as an integral part in achieving that purpose. Aquinas attempts to explain the totality of universal existence of the soul, the existence of God, and Catholic doctrines through a rationalistic view.Aquinas attempts to explain the nature of the human soul by positing seven questions coupled with several objections in order to clearly define the soul’s nature. These questions ask whether the soul is a body and whether the soul is a subsistence. Aquinas’ inquiry is furthered into the question of the souls of brute animals, if man’s soul is composed of body, soul, matter, and form. The last two questions inquire on the soul’s corruptibility and its comparison to the species of angels. First, Aquinas asks whether the soul is a body and poses the following objections. The soul is a body since the soul is the foremost moving principle and the body cannot act without a soul. Thus, if there is a thing that moves but not moved, according to Aquinas, that thing is the main cause of eternal movement. Hence, Aquinas proves that the soul is a body since the soul is a mover that is moved, and every mover moved possesses a body.To further the objection, Aquinas elaborates that knowledge is caused by likeness that is integral in assuming corporeal things. “If, therefore, the soul were not a body, it could not have knowledge of corporeal things” (Aquinas 663). The nature of the soul then is defined as the main principle or essence that is present in all things that live, which Aquinas calls as animate, meaning having a soul. The inanimate are those that have no life. Life is separated by knowledge and movement. Furthermore, Aquinas criticizes the ancient philosophers of having to maintain the ideal that the soul is corporeal or specified in the physical aspect. “The philosophers of old, not being able to rise above their imagination, supposed that the principle of these actions was something corporeal; for they asserted that only bodies were real things, and that what is not corporeal is nothing…”(Aquinas 663). The ancient philosophers (the pre-Platonics, Socrates, Plato, and Aristotle) defined the soul as a material essence as a part of the universal order. If the soul is not corporeal or bordered by physical matter, then it cannot be construed as something real. Aquinas rejects this statement by manifesting the difference between the body and soul. “For it is clear that to be a principle of life, or to be a living thing, does not belong to a body as such; since of, that were the case, every body would be a living thing, or a principle of life” (Aquinas, 664). Thus, the soul is the act of the body, since the body in itself is the first principle that defines life.Aquinas attempts to differentiate the soul between the animate and inanimate as well as the rational and irrational souls. Unique to human beings, man has will of reason or the ability to conceptualize choice. This will of reason is also the rational appetite of the individual that attempts to fulfill its purpose and attaining the good. In addition, Aquinas answers his first objection through the soul as something that is moved. Everything that moves is definitely moved by something else but not every mover is moved. Thus, certain things remain stationary or permanent as an effect of preceding causes. This explains the nature of the soul as a thing that is not essentially moved but moved accidentally. The body is then a thing that is moved inessentially, contrary to the soul. To be moved means that the soul passes from being a potential to being real or actual. The soul transcends from bodily knowledge through the intellect – immaterial and universal. However, God is the source of understanding and therefore is the only being capable of true understanding. Furthermore, the soul is divided into the cognitive soul, wherein it has the choice of forming understanding and sensation. Contrary to Plato’s Theory of Forms where knowledge is derived, Aquinas argues that real knowledge comes from God: “Now participated existence is limited by the capacity of the participator, so that God alone, who is his own existence, is pure act and infinite” (Aquinas, 671). Knowledge is then formed through the combination of the potential or passive senses (body) and the active or actual intellect (soul).On the question of the soul’s subsistence, Aquinas equates the soul as an act of understanding, meaning that the soul is the action of the body. Thus, the soul necessarily becomes incorporeal (separate from the body) and subsistent. Man can only understand the nature of all physical things through the body. “For it is clear that by means of the intellect, man can have knowledge of all corporeal things. Now whatever knows certain things cannot have any of them in its own nature; because that which is in it naturally would impede the knowledge of anything else” (Aquinas, 665). Man’s experiences are then dependent on the body, which is the only avenue in understanding the physical knowledge, different from the understanding of the soul. Similar to the foremost arguments and objections, man’s soul is rational, and thus separates itself from that of animalistic reason. “The body is necessary for the action of the intellect, not as its origin of action, but on the part of the object; for the phantasm is to the intellect what color is for sight” (Aquinas, 666). Thus, these mental images are essential in acquiring knowledge as well as utilizing the use of sense experience in order to abstract such forms for understanding.On the notion of the soul’s incorruptibility, Aquinas argues that the soul may be corrupted in two ways: per se and accidentally. He argues that any substance that can be corrupted accidentally is impossible since corruption is considered as a thing, along with existence. “Therefore, whatever has existence ‘per se’ cannot be generated or corrupted except ‘per se’; while things which do not subsist, such as accident and material forms, acquire existence or lost through the generation or corruption of composite things” (Aquinas, 672). Man’s soul is then dependent on the subjective sensual experience that the individual experiences everyday in attaining the ideal since man is created in the image and likeness of God. The passage also implies causal explanations towards the nature of man’s choice—that every actions constitutes a reaction that necessarily ‘corrupts’ the soul of man. This corruption comes from man itself and not from another generation or cause. The soul remains pure while the body experiences corruption because of misleading sensual experiences that does not act as universals. In addition, Aquinas adds that even though the soul may be composed by matter and form, it still remains incorruptible for corruption possesses contradiction. “Since generation and corruption are from contraries and into contraries. Wherefore the heavenly bodies, since they have no matter subject to contrariety, are incorruptible…there can be nor contrariety in the human soul for it receives according to the manner of its existence…” (Aquinas 673).The attainment of knowledge lies in the nature of man’s soul where the intellectual capability of the individual is a separate entity from that of the soul while remaining a part of the soul. The soul is also the capacity to reason, a similar term used by Platonic philosophers and the like as a means of attaining knowledge. Aquinas shares the same similarities with Aristotle as man’s essence is its rationality. However, Aquinas does not total man’s entirety with rationality, contrary to Aristotle. In addition, Aquinas also rejects the nature of innate ideas of Plato since the physical mind forms ‘phantasms’ that are derived mental images from sensual experience. From this, human being form passive knowledge from experience and the soul forms active knowledge. “Further, if the soul were subsistent, it would have some operation apart from the body. However, it has no operation apart from the body, not even that of understanding; for the act of understanding does not take place without a phantasm, which cannot exist apart from the body” (Aquinas, 665). These phantasms are not considered as universal knowledge since there is would be subjectivism instead of an objective standard of truth. According to Aquinas, God is the only source of knowledge contrary to a subjective sensual experience which contradicts the notion of an objective truth.The soul is then a reaction, the unmoved object that grants substantial truth as it relates itself to the function of the body. Moreover, the body is also an integral part of knowledge, as it provides sensual experience that directly hands abstractions. Though sensual experience does not necessitate in becoming universal knowledge, the soul’s active intellect filters the passive knowledge of the body into one. However, even though sense experience is necessary in formulation phantasms or mental images of an object as well as a universal concepts that applies to all things, it is impossible to have knowledge of a particular material object because there is already a conception of a mental image of it. Though the way to know the essence of a physical object is through abstraction, we cannot entirely have a real grasp of what that object is. All knowledge then is necessitated as abstract. This abstraction process leads to the use of scientific knowledge where there is an inkling of knowledge through cause and effect. On the other hand, it remains that the intellect has limitations with regard to abstract knowledge. We may have a concept or a grasp of what is sweet or sour through experience but we can never understand the real meaning of sweetness and sourness in itself.