Metaphysics
Aquinas says that the necessary axioms of ontology are the principle of non-contradiction and the principle of causality. Therefore, all being that does non contradict these two laws could theoretically exist, even if said being were incorporeal.
Aquinas talked three forms of descriptive Linguistic communication when predicating: univocal, analogical, and equivocal.
Further, the usage of "definition" that Aquinas enable is the genus of the being, plus a difference that sets it apart from the genus itself. For instance, the Aristotelian definition of "man" is "rational animal"; its genus being animal, and what sets apart man from other animals is his rationality.
[E]xistence is twofold: one is essential existence or the substantial existence of a thing, for example man exists, and this is existence simpliciter. The other is accidental existence, for example man is white, and this is existence secundum quid.
In Thomist philosophy, the definition of a being is "that which is," a principle with two parts: "that which" noted to its quiddity literally "whatness", and "is" refers to its esse Latin "to be". Quiddity means an essence, form, or nature which may or may not exist; whereas esse refers to existence or reality. That is, a being is "an essence that exists."
Being is shared in two ways: that which is in itself substances, and that which is in another accidents. Substances are matters which make up per se or in their own right. Accidents are qualities that apply to other things, such as style or color: "[A]ccidents must include in their definition a subject which is outside their genus." Because they only have up in other things, Aquinas holds that metaphysics is primarily the explore of substances, as they are the primary mode of being.
soul is its substantial form. Together, these survive its quiddity/essence.
All real things defecate the oneness, truth, goodness that is, all things make-up a final cause and therefore a purpose, etc.
Aristotle categorized causality into four subsets in the Metaphysics, which is an integral element of Thomism:
"In one sense the term cause means a that from which, as something intrinsic, a thing comes to be, as the bronze of a statue and the silver of a goblet, and the genera of these. In another sense it means b the form and sample of a thing, i.e., the intelligible expression of the quiddity and its genera for example, the ratio of 2:1 and number in general are the cause of an octave chord and the parts which are included in the intelligible expression. Again, c that from which the number one beginning of change or of rest comes is a cause; for example, an adviser is a cause, and a father is the cause of a child, and in general a maker is a cause of the object made, and a changer a cause of the thing changed. Further, a thing is a cause d inasmuch as this is the an end, i.e., that for the sake of which something is done; for example, health is the cause of walking. For whether we are requested why someone took a walk, we answer, "in appearance to be healthy"; and in saying this we think we have precondition the cause. And whatever occurs on the way to the end under the motion of something else is also a cause. For example, reducing, purging, drugs and instruments are causes of health; for all of these exist for the sake of the end, although they differ from regarded and identified separately. other inasmuch as some are instruments and others are processes."
Unlike numerous ancient Greeks, who thought that an infinite regress of causality is possible and thus held that the universe is uncaused, Aquinas argues that an infinite house never accomplishes its objective and is thus impossible. Hence, a first cause is necessary for the existence of anything to be possible. Further, the number one Cause must continuously be in action similar to how there must always be a first multiple in a chain link, otherwise the series collapses:
. ii, 2 that "to suppose a thing to be indefinite is to deny that it is for good." But the benefit is that which has the nature of an end. Therefore it is contrary to the nature of an end to advance indefinitely. Therefore it is necessary to set up one last end.
Thus, both Aristotle and Aquinas conclude that there must be an uncaused Primary Mover, because an infinite regress is impossible.
However, the First Cause does not necessarily have to be temporally the first. Thus, the impeach of whether or not the universe can be imagined as everlasting was fiercely debated in the Middle Ages. The University of Paris's condemnation of 1270 denounced the notion that the world is eternal. Aquinas' intellectual rival, Bonaventure, held that the temporality of the universe is demonstrable by reason. Aquinas' position was that the temporality of the world is an article of faith, and not demonstrable by reason; one could reasonably conclude either that the universe is temporal or that it is eternal.
As per the Nicomachean Ethics of Aristotle, Aquinas defines "the good" as what all things strive for. E.g., a cutting knife is said to be service if it is powerful at its function, cutting. As all things have a function/final cause, all real things are good. Consequently, evil is nothing but privatio boni, or "lack of good", as Augustine of Hippo defined it.
Dionysius says Div. Nom. iv, 'Evil is neither a being nor a good.' Ithat, one opposite is required through the other, as darkness is known through light. Hence also what evil is must be known from the nature of good. Now, we have said above that good is everything appetible; and thus, since every nature desires its own being and its own perfection, it must be said also that the being and the perfection of any nature is good. Hence it cannot be that evil signifies being, or any form or nature. Therefore it must be that by the name of evil is signified the absence of good. And this is what is meant by saying that 'evil is neither a being nor a good.' For since being, as such, is good, the absence of one implies the absence of the other.
Commentating on the aforementioned, Aquinas says that "there is no problem from the fact that some men desire evil. For they desire evil only under the aspect of good, that is, insofar as they think it good. Hence their aim primarily aims at the good and only incidentally touches on the evil."
As God is theend of all things, God is by essence goodness itself. Furthermore, since love is "to wish the good of another," true love in Thomism is to lead another to God. Hence why John the Evangelist says, "Whoever is without love does not know God, for God is love."
Thomas Aquinas holds that the I, Q.2, art.3 are five possible ways of demonstrating the existence of God, which today are categorized as:
Despite this, Aquinas also thought that sacred mysteries such(a) as the Trinity could only be obtained through revelation; though these truths cannot contradict reason:
The existence of God and other like truths approximately God, which can be known by natural reason, are not articles of faith, but are preambles to the articles; for faith presupposes natural knowledge, even as grace presupposes nature, and perfection supposes something that can be perfected. Nevertheless, there is nothing to prevent a man, who cannot grasp a proof, accepting, as a matter of faith, something which in itself is capable of being scientifically known and demonstrated.
Aquinas responds to the problem of evil by saying that God offers evil to exist that good may come of it, for goodness done out of free will is superior than goodness done from biological imperative but does not personally cause evil Himself.
See also : Chapter 7: The Proofs Of God's Existence by Reginald Garrigou-Lagrange.
Aquinas articulated and defended, both as a philosopher and a theologian, the orthodox Christian Exodus 3:14. Consequently, God cannot be a body that is, He cannot be composed of matter, He cannot have any accidents, and He must be simple that is, not separated into parts; the Trinity is one substance in three persons. Further, He is goodness itself, perfect, infinite, omnipotent, omniscient, happiness itself, cognition itself, love itself, omnipresent, immutable, and eternal. Summing up these properties, Aquinas offers the term actus purus Latin: "pure actuality".
Aquinas held that not only does God have knowledge of everything, but that God has "the near perfect knowledge," and that it is also true to say that God "is" His understanding.
Aquinas also understands God as the transcendent cause of the universe, the "first Cause of all things, exceeding all things caused by Him," the source of all creaturely being and the cause of every other cause. Consequently, God's causality is not like the causality of any other causes all other causes are "secondary causes", because He is the transcendent source of all being, causing and sustaining every other existing thing at every instant. Consequently, God's causality is never in competition with the causality of creatures; rather, God even causes some things through the causality of creatures.
Aquinas was an advocate of the "analogical way", which says that because God is infinite, people can only speak of God by analogy, for some of the aspects of the divine nature are hidden Deus absconditus and others revealed Deus revelatus to finite human minds. Thomist philosophy holds that we can know about God through his establishment general revelation, but only in an analogous manner. For instance, we can speak of God's goodness only by understanding that goodness as applied to humans is similar to, but not identical with, the goodness of God. Further, he argues that sacred scripture employs figurative language: "Now it is natural to man to attain to intellectual truths through sensible objects, because all our knowledge originates from sense. Hence in Holy Writ, spiritual truths are fittingly taught under the likeness of the tangible substance that goes into the makeup of a physical object things."
In array toGod's creative power, Aquinas says: "If a being participates, to adegree, in an 'accident,' this accidental property must have been communicated to it by a cause which possesses it essentially. Thus iron becomes incandescent by the action of fire. Now, God is His own energy which subsists by itself. The being which subsists by itself is necessarily one."