- What is it: Natural Law in Philosophy
- What is it: Despair in Philosophy
- Who he is: Diógenes Laércio in Philosophy
- What is it: Difference in Philosophy
- What is it: Causal Determinism in Philosophy
- Who is: Dworkin, Ronald in Philosophy
- What is it: Property Dualism in Philosophy
- Who is: Durkheim, Émile in Philosophy
- What is it: Dogma in Philosophy
- Who is: Dennett, Daniel in Philosophy
- What is it: Division in Philosophy
- Who is: Dilthey, Wilhelm in Philosophy
- What is it: Dialetheism in Philosophy
- Who is he: Democritus in Philosophy
- What is it: Human Rights in Philosophy
- Who he is: Damásio, António in Philosophy
- What is it: Doubt in Philosophy
- Who is: Dummett, Michael in Philosophy
- What is it: Disjunctivism in Philosophy
- Who he is: Diogenes of Sinope in Philosophy
- What is it: Discourse in Philosophy
- Who he is: Derrida, Jacques in Philosophy
- What is it: Deconstructionism in Philosophy
- Who is: Danto, Arthur in Philosophy
- What is it: Dasein in Philosophy
- Who is it: Deleuze, Gilles in Philosophy
- What is it: Deontology in Philosophy
- Who is: Davidson, Donald in Philosophy
- What is it: Democracy in Philosophy
- Who is: Dun Scotus, John in Philosophy
- What is it: Dualism in Philosophy
- Who is it: Dretske, Fred in Philosophy
- What is it: Dogmatism in Philosophy
- Who is: Diderot, Denis in Philosophy
- What is it: Dialectics in Philosophy
- Who is: Dewey, John in Philosophy
- What is it: Determinism in Philosophy
- Who is: Descartes, René in Philosophy
- What is it: Deduction in Philosophy
- What is it: Discovery of Truth in Stoicism
- What is it: Determination in Stoicism
- What is it: Development of Autarchy in Stoicism
- What is it: Self-Mastery in Stoicism
- What is it: Dedication to Virtue in Stoicism
- What is it: Willingness to Learn in Stoicism
- What is it: Emotional Discipline in Stoicism
- What is it: Mental Discipline in Stoicism
- What it is: Development of Resilience in Stoicism
- What is it: Moral Duty in Stoicism
- What is it: Moral Direction in Stoicism
- What is it: Character Development in Stoicism
- What is it: Devotion to Stoicism
- What is it: Decency in Stoicism
- What is it: Spiritual Development in Stoicism
- What is it: Contempt in Stoicism
- What is it: Development of Virtue in Stoicism
- What is it: Discovery of Self in Stoicism
- What is it: Personal Development in Stoicism
- What is it: Diligence in Stoicism
- What is it: Dogmatism in Stoicism
