Philosophy Fundamentals: Key Concepts & What You Need to Know

Philosophy isn't abstract academic exercise—it's practical wisdom for living an examined life. The questions philosophers have wrestled with for millennia remain urgently relevant: How do we know what's true? What makes an action right or wrong? Do we have free will? What is consciousness? These aren't idle puzzles but the foundations of how we navigate decisions, evaluate arguments, and construct meaning.

This guide breaks down the essential concepts of philosophy. You'll learn the Socratic method for exposing hidden assumptions, major ethical frameworks for moral reasoning, logical tools for constructing and evaluating arguments, and the persistent questions about mind, knowledge, and meaning that shape modern debates about AI, medical ethics, and personal purpose.

Start practicing philosophy fundamentals ▸

What is the Socratic method and how does it work?

The Socratic method reveals hidden assumptions through four key questions: "What do you mean by X?" (clarification), "What evidence supports that?" (justification), "What would someone who disagrees say?" (counterargument), and "What follows if that's true?" (implications). This questioning sequence systematically exposes contradictions in beliefs we've never examined.

The method works because it moves progressively deeper. When someone claims "money brings happiness," asking what they mean by happiness reveals they might actually mean security or pleasure. Demanding evidence exposes anecdotal thinking. Considering opposing views highlights cherry-picking. Following implications often reveals the initial claim contradicts other beliefs they hold. This systematic approach transforms vague opinions into examined positions.

What is Socratic irony and why is it effective?

Socratic irony—claiming "I know that I know nothing" while questioning others—transforms philosophical discussion from combat to collaboration. By positioning yourself as genuinely confused rather than superior, you remove ego from the conversation. People feel like they're teaching you rather than being attacked, which opens them to examining their own beliefs without defensiveness.

This psychological technique works because people resist direct challenges but enjoy explaining their views. Instead of "You're wrong about immigration," try "I'm confused about immigration policy—help me understand your view." The same probing questions feel helpful rather than hostile, making people more likely to discover contradictions themselves rather than dig in against attack.

What is elenchus and what is aporia?

The elenchus (Socratic refutation) follows a predictable pattern: clarify the claim, draw out logical implications, identify contradictions with other beliefs, then reach aporia (productive confusion). This pattern works like intellectual judo, using opponents' certainty against them. Someone claims "lying is always wrong." You draw implications: "So hiding Jews from Nazis was wrong?" They realize their position contradicts other moral beliefs.

Aporia isn't destructive confusion but productive puzzlement. The person thought they knew; now they know they don't know. Socrates saw this uncomfortable state as wisdom's beginning—it motivates genuine inquiry rather than defending predetermined positions. Understanding how to guide conversations toward aporia without creating hostility is a skill that takes practice to internalize. Loxie helps reinforce the distinctions between types of assumptions and the questioning strategies for each.

Practice the Socratic method ▸

What is Descartes' method of radical doubt?

Descartes' radical doubt methodically strips away uncertain beliefs to find an indubitable foundation for knowledge. First, he doubts the senses—optical illusions prove they're unreliable. Then he doubts physical reality—dreams feel real while you're having them. Finally, he even doubts mathematics—an evil demon could be deceiving us about the most basic truths. This systematic doubt leaves only one certainty: "cogito ergo sum" (I think, therefore I am).

The cogito resists all doubt because doubting requires thinking, and thinking proves the existence of a thinker. Even if everything else is illusion, the illusion requires an experiencer. Try to doubt your existence—that very doubt proves you exist as the doubter. This gives one absolute certainty from which to rebuild knowledge. Modern philosophy starts here, with consciousness as the undeniable given.

Reading about Descartes is different from thinking like Descartes
The distinction between the cogito's logical structure and its significance takes repeated engagement to fully grasp. Loxie uses spaced repetition to help you internalize these philosophical foundations until they become second nature.

Build philosophical foundations ▸

What is Kant's categorical imperative?

Kant's categorical imperative tests morality through universalizability: "Act only according to maxims you could will to become universal laws." This means an action is moral only if everyone could do it without logical contradiction. Lying fails this test because universal lying destroys the trust that makes lying possible—if everyone lied, no one would believe anyone, making lies pointless.

Consider lying to get a loan: if everyone lied for loans, no one would lend, making loans impossible, thereby defeating your original purpose. The contradiction isn't about consequences but logic—universal lying is self-defeating. Similarly, breaking promises fails because universal promise-breaking eliminates promises entirely. This framework gives objective moral standards without religious commands or utilitarian calculations, grounding ethics in reason itself.

What is Kant's humanity formulation?

Kant's second formulation states: "Treat humanity never merely as means but always as an end." This prohibits using people as tools for your purposes without respecting their autonomous choices. Hiring someone respects their autonomy (they choose to work), but deceiving them for gain treats them as mere tools. Even benevolent manipulation violates this principle—lying to someone "for their own good" denies their rational autonomy.

This explains why consent matters morally and why coercion is wrong even with good intentions. The principle makes human dignity fundamental to ethics—not dependent on consequences or social agreements but intrinsic to rational beings. Remembering the distinction between Kant's universalizability test and his humanity formulation requires active recall practice, which Loxie provides through targeted questions.

What is Nietzsche's will to power?

Nietzsche's will to power reinterprets all human motivation as the drive for growth, mastery, and self-overcoming rather than pleasure or survival. Artists creating despite poverty, athletes training through pain, and entrepreneurs risking security all manifest this fundamental life force. We don't fundamentally seek happiness—we seek to become more, to expand our capabilities.

This concept explains behaviors that hedonism and survival instinct can't explain. Why do people choose difficult challenges over comfortable lives? Why create art nobody might see? Why climb mountains? The will to power says humans fundamentally seek expansion of capabilities, not just pleasant feelings. This drive appears in healthy forms (creativity, achievement) and unhealthy ones (domination, cruelty). Understanding this motivation explains why easy lives often feel empty and why humans need challenges to thrive.

What does Nietzsche mean by "God is dead"?

Nietzsche's "God is dead" diagnoses the collapse of traditional meaning structures—it's not celebrating atheism but warning about what happens when religious frameworks providing purpose and values crumble. For millennia, religion provided ready-made purpose, moral codes, and cosmic significance. Without God, who determines right and wrong? What makes life meaningful?

Nietzsche saw most people couldn't handle this freedom, predicting nihilistic despair. His solution—become the "overman" who creates values authentically—requires strength few possess. This insight predicted 20th-century existentialism and explains modern meaning crises. When traditional structures collapse, humans face the burden of self-creation without cosmic guarantee. The "problem of nihilism" becomes personal: without transcendent meaning, you must create significance or sink into despair.

Master Nietzsche's key concepts ▸

What are the major ethical frameworks?

Four major ethical frameworks dominate moral philosophy: utilitarianism (consequences determine rightness), deontology (duties and rules determine rightness), virtue ethics (character determines rightness), and existentialist ethics (authentic choice determines rightness). Each framework produces different conclusions about the same moral dilemmas, which is why understanding all four is essential for navigating ethical complexity.

What is utilitarianism?

Utilitarianism calculates morality by measuring consequences—the right action produces the greatest good for the greatest number. This makes lying to save lives potentially moral and extreme self-sacrifice obligatory if it maximizes overall well-being. Donating to charity until you're as poor as those you're helping becomes obligatory if each dollar helps them more than you.

Act utilitarianism judges each action separately, while rule utilitarianism follows rules that generally maximize good. This explains why rule utilitarians might prohibit lying even to save lives, since universal honesty creates more overall benefit despite occasional tragic cases. Critics argue utilitarianism makes morality too demanding and allows injustice if it benefits the majority. But utilitarians respond that moral truth isn't always comfortable.

What is deontological ethics?

Deontological ethics judges actions by adherence to moral duties regardless of consequences. Lying remains wrong even to save lives because it violates the duty of truthfulness and treats others as mere means rather than autonomous agents deserving respect. Consequences don't determine rightness—duty does.

The doctrine of double effect distinguishes intended consequences from merely foreseen ones—bombing military targets knowing civilians will die differs morally from targeting civilians, even with identical death tolls, because intention determines moral character. This explains moral intuitions like "torture is wrong" even if it could save thousands. Critics call this rigid, but deontologists say moral principles shouldn't bend to circumstances.

What is virtue ethics?

Virtue ethics focuses on character rather than acts or rules—asking "what would a virtuous person do?" and emphasizing cultivation of excellences like courage, temperance, and practical wisdom through repeated practice until they become natural. The virtuous person naturally does right because their character is properly formed.

Aristotle's doctrine of the mean locates virtue between extremes—courage lies between cowardice and recklessness, generosity between stinginess and profligacy. Practical wisdom (phronesis) determines the right balance for each situation rather than following rigid formulas. This explains why ethics can't be reduced to rules—judgment requires wisdom that comes only through practice.

What is existentialist ethics?

Existentialist ethics grounds morality in radical freedom and authenticity. Without predetermined essence, humans create meaning through choices. "Bad faith"—denying your freedom by pretending you have no choice—becomes the fundamental moral failure. The waiter who over-identifies with his role, the woman who pretends not to notice flirtation—both flee from freedom's anxiety.

Authenticity means owning your choices and their consequences. You're "condemned to be free" as Sartre described—no God, nature, or reason determines right and wrong. This makes responsibility absolute but morality individual. You can't blame anyone or anything for who you become. Camus's Sisyphus exemplifies this: condemned to push a boulder eternally, he becomes heroic by choosing to embrace his fate with full awareness.

Practice distinguishing ethical frameworks ▸

What does the trolley problem reveal about ethics?

The trolley problem reveals how different ethical frameworks produce opposite conclusions. Utilitarians pull the lever to save five by killing one. Deontologists refuse because killing violates moral duty. Virtue ethicists consider character implications. Existentialists emphasize choosing without universal guidance. The problem exposes the frameworks we unconsciously apply.

Most people would pull a lever to divert a trolley from five people to one (utilitarian reasoning), but wouldn't push a fat man off a bridge to stop the trolley (deontological intuition against direct killing). This inconsistency reveals we use multiple ethical frameworks simultaneously without realizing it. Variations expose more intuitions: what if the one person is a child? A criminal? Your mother? Each framework gives different answers, showing why moral philosophy remains contentious despite millennia of debate.

What are the most common logical fallacies?

Logical fallacies are errors in reasoning that undermine arguments. Understanding common fallacies helps you evaluate claims critically and construct stronger arguments yourself. Three particularly prevalent fallacies are the straw man, ad hominem, and false dichotomy.

What is the straw man fallacy?

The straw man fallacy misrepresents opponents' positions to make them easier to attack—turning "we should regulate guns" into "they want to ban all guns" or "we need police reform" into "they want anarchy." You defeat a fabricated argument rather than the actual one. This works by exaggeration and simplification: take a nuanced position, strip away qualifications, amplify to absurdity, then attack that distortion.

The defense is simple: "That's not what I said. Here's my actual position." Recognizing straw men requires knowing actual positions, not caricatures. Politicians use this constantly—any tax becomes "socialism," any deregulation becomes "corporate anarchy."

What is ad hominem?

Ad hominem attacks target the person making an argument rather than the argument itself—dismissing ideas based on the speaker's character, credentials, or associations. "You can't talk about poverty, you're rich" or "Your opinion on war doesn't count, you didn't serve" both avoid the actual argument. Even "Hitler was vegetarian" is irrelevant to evaluating vegetarianism.

The fallacy confuses source with validity. A hypocrite can speak truth; a saint can be wrong. Good ideas can come from bad people; bad ideas from good people. Focus on the argument's logic and evidence, not who's making it.

What is a false dichotomy?

False dichotomies present only two options when more exist—"you're either with us or against us" or "love it or leave it." This forces choice between extremes while hiding moderate positions, nuanced views, or creative alternatives. Reality rarely offers just two choices. Between capitalism and communism lie mixed economies. Between belief and atheism lies agnosticism.

The fallacy works by making fence-sitting seem impossible and forcing people into camps. Recognizing false dichotomies means looking for hidden third options and rejecting forced binary choices.

What is the difference between valid and sound arguments?

Valid arguments have conclusions that necessarily follow from premises regardless of whether those premises are true. Sound arguments are both valid and have true premises. This distinction separates logical structure from factual accuracy. "All fish fly, Nemo is a fish, therefore Nemo flies" is valid but unsound—the conclusion follows logically, but the premises are false.

Testing validity requires assuming premises are true then checking if the conclusion must follow. If you can imagine premises being true while the conclusion is false, the argument is invalid. "Some dogs are brown, Fido is brown, therefore Fido is a dog" has true premises and a plausible conclusion but invalid structure—Fido could be a cat. Master this distinction and you'll spot bad reasoning everywhere.

How do you identify hidden premises?

Hidden premises are unstated assumptions required for arguments to work. They often represent the weakest points since people rarely examine or defend them. "We should ban violent video games because they cause aggression" assumes aggression is bad and government should regulate harmful media. Neither assumption is defended.

To find hidden premises, ask what must be true for the conclusion to follow from stated premises. Making these explicit often reveals that disagreement isn't about stated claims but unstated assumptions. This technique transforms vague disagreements into precise philosophical differences that can actually be resolved.

What is the difference between deductive and inductive reasoning?

Deductive arguments claim certainty—conclusions are guaranteed by premises. "All humans are mortal, Socrates is human, therefore Socrates is mortal" preserves truth from premises to conclusion. Inductive arguments claim probability—conclusions are supported by evidence but not guaranteed. "The sun has risen every day, so it will rise tomorrow" extends from observations but can't achieve certainty.

Deduction doesn't generate new knowledge, just reveals what's implicit in premises. Induction generates new knowledge by generalizing from experience but can never guarantee truth. All science uses induction—we assume natural laws won't change tomorrow. This explains why mathematics feels certain (deductive) while scientific theories remain provisional (inductive).

Practice identifying fallacies ▸

What is the free will debate?

Hard determinism claims every event including human actions results from prior causes in an unbreakable chain. Your choice to read this stems from brain states caused by genetics and experiences stretching back to the Big Bang, making free will an illusion and moral responsibility questionable. Every decision results from prior brain states, themselves caused by earlier states, in a causal chain you don't control.

The consequence argument makes this rigorous: you don't control the past or laws of nature; your current actions result from past states plus natural laws; therefore, you don't control your current actions. This means criminals aren't evil but unlucky in their causal history. Heroes aren't praiseworthy but fortunate. The argument's power lies in its simplicity.

What is compatibilism?

Compatibilism reconciles free will with determinism by redefining freedom. You're free when acting on your desires without external coercion, even if those desires are determined. A drug addict who wants drugs and takes them acts freely; one who wants to quit but can't lacks freedom. Both are determined, but internal conflict matters morally.

This position saves moral responsibility without denying science. Freedom doesn't require escaping causation but acting according to your own desires and reasoning. This matches legal intuitions—we distinguish crimes committed freely from those under coercion. Compatibilists say asking for non-determined free will is like asking for a square circle—conceptually confused rather than empirically false.

What is the hard problem of consciousness?

The hard problem of consciousness asks how physical brain processes create subjective experience—why there's "something it's like" to see red or taste coffee beyond mere information processing. We can explain how brains process color wavelengths, but not why red looks the way it does to you. That qualitative experience—what philosophers call qualia—seems to escape physical description.

Mary the color scientist knows all physical facts about color but experiences something new when first seeing red. This suggests consciousness involves more than physical processes. If true, uploading minds to computers might preserve information processing but lose subjective experience—creating philosophical zombies rather than conscious beings. The Chinese Room argument makes this vivid: following rules to produce Chinese outputs doesn't equal understanding Chinese.

What is knowledge and how do we know we have it?

Knowledge was traditionally defined as "justified true belief"—you must believe it, it must be true, and you must have good reasons. But Gettier cases show these conditions might not suffice. Imagine you see a sheep-shaped rock and believe "there's a sheep in the field." Unknown to you, a real sheep hides behind the rock. Your belief is true, justified, yet seems not to be knowledge—it's lucky accident.

Skeptical scenarios like brain-in-a-vat demonstrate the impossibility of certain knowledge about external reality. If you can't prove you're not in the Matrix, absolute certainty about the external world becomes logically unattainable. The problem of induction compounds this: just because the sun has always risen doesn't logically guarantee tomorrow's sunrise. Scientific knowledge rests on the unprovable assumption that nature remains uniform.

What is epistemic humility?

Epistemic humility means recognizing knowledge limitations without paralysis—accepting fallibility while acting on best evidence. The key is proportioning confidence to evidence. Mathematical theorems deserve near-certainty; scientific theories merit strong confidence; personal memories warrant moderate trust; future predictions require humility.

This framework helps navigate information overload—not all claims deserve equal skepticism or credence. Epistemic humility also means changing views when evidence shifts rather than defending positions dogmatically. It's intellectual honesty in practice.

What is Aristotle's concept of eudaimonia?

Aristotle's eudaimonia defines the good life as human flourishing through excellence—not mere happiness but actualizing potential through virtue, meaningful relationships, and contemplation. A plant flourishes by growing strong and bearing fruit, not by avoiding pain. Similarly, humans flourish by developing excellences: courage, wisdom, justice, friendship.

The function argument claims humans have a characteristic function like organs have functions. Just as eyes function to see well, humans function to reason and act virtuously, making excellence at these activities the path to flourishing. This provides objective standards for good life—not based on preference but human nature. Pleasure accompanies flourishing but isn't the goal. This explains why lottery winners aren't happier long-term and why meaningful struggle often brings more satisfaction than easy pleasure.

The real challenge with learning philosophy

Philosophy's concepts seem straightforward when you read them, but applying them is another matter. You might understand the categorical imperative intellectually but forget to test your decisions through universalizability when it matters. You might recognize straw man fallacies in examples but miss them in real-time conversation. The gap between reading about philosophy and thinking philosophically is the gap between knowing and doing.

Research on the forgetting curve shows we lose up to 70% of new information within 24 hours without reinforcement. How much of the distinction between valid and sound arguments will you remember next week? Can you reliably identify hidden premises in a month? Philosophy's power lies in having these frameworks available when you need them—and that requires more than one reading.

How Loxie helps you actually think philosophically

Loxie uses spaced repetition and active recall to help you internalize philosophical concepts so they're available when you need them. Instead of passively re-reading, you engage with targeted questions that resurface ideas right before you'd naturally forget them—the Socratic method's four questions, the distinction between deductive and inductive reasoning, the difference between utilitarianism and deontology.

Just 2 minutes of daily practice builds durable understanding. The free version includes Philosophy Fundamentals in its full topic library, so you can start transforming philosophical knowledge into philosophical thinking immediately. These frameworks aren't meant to sit in notes you'll never revisit—they're meant to shape how you evaluate arguments, make decisions, and examine your beliefs.

Sign up free and start retaining ▸