Key Concepts in Philosophy: From Plato to Aristotle

Posted on Jan 31, 2025 in Philosophy and ethics

Key Philosophical Terms and Concepts

Philosophy: Critical reasoning about ultimate questions. Modus Ponens: If A, then B. A. Therefore, B. Modus Tollens: If A, then B. Not B. Therefore, not A. Analogy: An argument that moves from one specific example to another, reasoning that because the two examples are alike in many ways, they are also alike in one further specific way. Epistemology: The subfield of philosophy that concentrates on what we can know. Metaphysics: The subfield of philosophy that concentrates on what is ultimately real. Relativism: The view that truth and goodness are solely relative to a human individual or culture; that a person or a culture is the sole arbiter of what is true and right. Asceticism: Abstention from all forms of self-indulgence; highly self-disciplined for the sake of achieving some single goal. Metempsychosis: The process whereby eternal souls transmigrate from body to body. Virtue (arete): The excellence of a thing; X is good when X performs its function well, and excellence is X being as good as possible (best). Happiness (eudaimonia): To flourish; to live well; not necessarily mere pleasure or a fleeting feeling.

Plato’s Argument on Justice and Health

Republic, Book IV

  1. All happy people are healthy people.
  2. No unjust people are healthy.

Therefore, no unjust people are happy.

The Analogy of the Sun

  • The act of seeing something requires three things: the eye, the object seen, and the sun, which is the light that illuminates the object in order for the eye to see.
  • Likewise, the act of knowing something requires three things: the soul (mind), the object known (truths in one’s understanding), and the form of the Good, which is the rational light that illuminates the rational object in order for the soul to know.
  1. The act of seeing is like the act of knowing.
  2. The sun is the condition of possibility for sight.
  3. The form of the Good is the condition of possibility for knowledge.

Aristotle’s Happiness Argument

Nicomachean Ethics, Book I, Chapters 1-5

  1. Every art or applied science (i.e., skill) and every systematic investigation (i.e., question), and similarly every action and choice aims at some good.
  2. If every skill, question, action, and choice aims at some good, then these things can be arranged into an order of means and ends.
  3. If every skill, question, action, and choice can be arranged into an order of means and ends, then there is some ultimate intrinsically good goal for a human which is never of instrumental value but from which all instrumental values derive their worth.
  4. “Happiness” (eudaimonia; flourishing or living well; do not equate with mere pleasure) is the word that human beings use to refer to the ultimate intrinsically good goal for a human which is never of instrumental value but from which all instrumental values derive their worth.
  5. There is an ultimate intrinsically good goal for a human which is never an instrumental value but from which all instrumental values derive their worth and this is called “happiness.”

The Function and Pleasure Arguments

Nicomachean Ethics, Book I, Chapter 7

1st Principle (definition: “function”): If only an X and every X can do F, then F is the function of X.

2nd Principle (definition: “good”): X is good only if X performs F well.

  1. Only humans and all humans are, by definition, rational.
  2. Living a rational life is the function of the human being. {1, 1st Principle}
  3. The good human being is one that lives rationally excellently. {2, 2nd Principle}
  1. Non-human animals experience mere pleasure.
  2. Pleasure cannot be the function of a human being. {1, 1st Principle}
  3. Pleasure cannot be the ultimate human good. {2, 2nd Principle}

Arguments Against Pleasure as the Ultimate Good

  1. Pleasure can be bad.
  2. Goodness cannot be bad.
  3. Pleasure cannot be goodness.
  1. If pleasure depends on the activity that produces it, then figuring out which pleasures are choiceworthy requires that we first figure out which activities are choiceworthy.
  2. Pleasure depends on the activity that produces it.
  3. Figuring out which pleasures are choiceworthy requires that we first figure out which activities are choiceworthy.
  1. All activities that constitute the proper function of a human being are choiceworthy activities for a human being.
  2. Rational activities constitute the proper function of the human being.
  3. Rational activities are the choiceworthy activities for a human being.