#apologetics #geisler
***The importance of the First Principles***
Aquinas believes that all knowledge is based on basic undeniable principles that provide the foundation for sure knowledge. Without these first principles there can be no true knowledge. As he puts it, “perfect knowledge requires certitude, and this is why we cannot be said to know unless we know what cannot be otherwise.”
1. _T**he Principle of Non-contradiction**__._
1. The ontological aspect of this principle may be stated in several ways: “being is not nonbeing”; “it is necessary that being not be nonbeing”; and “it is impossible that being be nonbeing.” Epistemologically, there are at least two ways to express this principle: (1) it is impossible that contradictory statements be simultaneously true; (2) if one contradiction is true, the other is necessarily false.11 Aquinas justifies this principle by pointing out that being is intelligible; nonbeing is unintelligible and whoever denies this uses it to make an intelligible statement.
2. ***The Principle of Identity.***
1. In the order of being (ontology) Aquinas states this principle in several ways: “being is being”; “every being is necessarily what it is”; “everything is identical with itself”; and “being and one are convertible.” Fundamentally, the principle of identity signifies the unity of things.
3. ***The Principle of Excluded Middle***.
1. This principle is the principle of either/or. Ontologically, something must either be or not be. It cannot both be and not be at the same time and in the same sense.
4. _**The Principle of Causality. Ontologically***.
1. the principle of causality is limited in its application to the realm of finite, contingent beings. In this regard, “everything which is capable of existing or not existing has some cause; because considered in itself it is indifferent to either alternative, and thus there has to be something else which determines it to be.” Therefore, “since there can be no process into infinity there has to be something necessary, which is the cause of all things capable of existing or not existing.”14 In general, then, causality says “everything contingent is caused.” Or “every efficient action, which is a passage from potency to act, is caused.” Since it is contingent, it is possible for it to not be, and therefore it is caused or dependent on another.
5. ***The Principle of Finality***.
1. “Every agent acts for an end.” This principle of finality (or teleology) is the one Aquinas uses to develop many of his great metaphysical and epistemological theses. In its ontological form, finality states that “being as agent is finalized.” He wrote, “I answer that it is in the nature of every act to communicate itself as far as possible.”16 To act for an end is to communicate oneself.
Aristotle lists several arguments of this kind in defense of the first principle of non-contradiction:
1. To deny it would deprive words of their fixed meaning and render speech useless.
2. Reality of essences must be abandoned. There would be becoming without anything that becomes, flying without a bird, accidents without substance.
3. There would be no distinction between things. All would be one.
4. It would mean the destruction of truth, for truth and falsity would be the same.
5. It would destroy all thought, even opinion, for its affirmation would be its negation.
6. Desire and preference would be useless, for there would be no difference between good and evil.
7. Everything would be equally true and false at the same time. No opinion would be more wrong than any other, even in degree.
8. It would make impossible all becoming, change, or motion, for all this implies a transition from one state to another, but all states would be the same, if contradiction is not true.
Link: [The First Principles of Knowledge – NORMAN GEISLER](https://normangeisler.com/the-first-principles-of-knowledge/)