Definition, Branches, Method, and How to Write About It
It sounds like the easiest question in any intro course. It is not. “What is science?” is a question that philosophers, historians, and working scientists have argued about for centuries — and your professor knows that. Here is what the question is actually asking, how to answer it properly, and what students consistently get wrong when they try.
Most students answer “what is science?” by listing things science has produced — vaccines, the periodic table, black hole images. That is the wrong answer. Or at least it is an incomplete one. The question is not asking for outputs. It is asking about a process — a particular way of building knowledge that distinguishes science from philosophy, religion, art, and opinion. Get that distinction right and the assignment almost writes itself.
What This Guide Covers
A Working Definition of Science
Science is a systematic process for generating reliable knowledge about the natural and social world through observation, testing, and evidence. That is the short version. The longer version is more contested than most introductory courses let on.
The word itself comes from the Latin scientia, meaning knowledge. But not all knowledge is scientific. The defining feature of science is its method — not its subject matter and not its conclusions. Science is distinguished by the way it checks its own claims against reality. You form a hypothesis. You design a test. You collect data. You revise your hypothesis based on what the data says, whether or not you like what you find.
The Stanford Encyclopedia of Philosophy defines science as involving systematic empirical investigation of the natural world and the construction of theories to explain and predict phenomena. Crucially, it notes the definition is contested — what counts as “scientific” has been debated across the history of the discipline itself, and there is no single agreed demarcation criterion. This matters for your essay. Do not present science as having one clean, uncontroversial definition. It does not.
One useful framing: science is both a body of knowledge (the accumulated results of scientific investigation) and a method (the process by which that knowledge is generated and revised). Your assignment will almost always want you to address both, even if it only asks for “a definition.”
The Three Major Branches
Science is not one thing. It splits into three major domains, each with different methods, objects of study, and standards for evidence.
Natural Sciences
Study the physical and biological world. The natural sciences are what most people picture when they hear the word “science.” They rely on controlled experiments, measurement, and mathematical modelling.
- Physics — matter, energy, forces, space-time
- Chemistry — elements, compounds, reactions
- Biology — living organisms and their systems
- Earth and space sciences — geology, astronomy, ecology
Social Sciences
Study human behaviour, societies, institutions, and cultures. More contested in terms of method — social scientists debate whether the experimental model of natural science is always appropriate for human subjects.
- Psychology — individual behaviour and cognition
- Sociology — group behaviour and social structures
- Economics — resource allocation and decision-making
- Political science — power, governance, and policy
Formal Sciences
Use logic and abstract systems rather than empirical observation. Mathematics is the obvious example — a mathematical proof is not scientific in the empirical sense because it does not depend on running experiments or gathering data from the world. But formal sciences underpin all the others: you cannot do physics without calculus, and you cannot do psychology without statistics.
- Mathematics — quantity, structure, space, change
- Logic — rules of valid inference
- Statistics — collection, analysis, and interpretation of data
- Computer science — computation and information theory
Engineering, medicine, agriculture, and environmental science are applied disciplines — they draw on natural and social science knowledge to solve practical problems. They are not a separate “branch” in the theoretical sense, but they are important enough that many assignments expect you to mention where pure and applied science differ. Pure science generates knowledge for its own sake. Applied science puts that knowledge to work.
| Branch | Primary Method | Example Disciplines | What It Studies |
|---|---|---|---|
| Natural Sciences | Controlled experiments, observation, measurement | Physics, chemistry, biology | The physical and biological world |
| Social Sciences | Surveys, case studies, statistical analysis, ethnography | Psychology, sociology, economics | Human behaviour and societies |
| Formal Sciences | Logical deduction, proof, abstraction | Mathematics, logic, statistics | Abstract systems and structure |
| Applied Sciences | Draws on all of the above | Engineering, medicine, computer science | Practical problem-solving |
The Scientific Method — Step by Step
The scientific method is the procedure science uses to move from question to reliable conclusion. It is not a rigid checklist — in practice, scientists loop back, revise, and jump steps. But the underlying logic is consistent.
Observation — Something Catches Your Attention
Science starts with noticing something in the world. It could be a pattern, an anomaly, or a gap in existing knowledge. The observation does not have to be dramatic. Isaac Newton did not watch an apple fall and immediately derive the law of gravitation — the observation triggered a question, and the work came after. The point is that science is grounded in the world, not in prior assumptions.
Question — What Is Actually Going On Here?
A good scientific question is specific and answerable. “Why is the sky blue?” is scientific. “What is the meaning of life?” is not — it cannot be answered with evidence and it does not produce testable predictions. Sharpening the question is more important than most students realise. A vague question produces a vague study and a vague conclusion.
Hypothesis — A Testable Proposed Answer
A hypothesis is not a guess. It is a specific, falsifiable prediction about what the data should look like if a particular explanation is correct. “Plants grow taller with more sunlight” is a hypothesis. “Plants grow better” is not — “better” is not measurable. Your hypothesis needs to be precise enough that an experiment could potentially prove it wrong.
Experimentation — Designing a Controlled Test
The experiment is designed to isolate the variable you are testing. Everything else is held constant. One group gets the treatment; one group does not. You measure the outcome. The reason for controls is straightforward — if you change three things at once, you cannot know which one caused the result. Control eliminates that ambiguity.
Analysis — What Does the Data Actually Say?
Data does not speak for itself. A scientist applies statistical methods to determine whether the results are likely due to the treatment or due to chance. A result that could easily have happened by chance is not evidence of anything. The threshold for “significant enough to take seriously” varies by field — medicine uses stricter standards than psychology, for reasons that have been the subject of serious debate in recent years.
Conclusion and Revision — What Do We Know Now That We Did Not Before?
A conclusion is not a final answer. It is an update to the state of knowledge. If the data supports the hypothesis, that is evidence for it — not proof. If the data contradicts the hypothesis, the hypothesis must be revised or abandoned. Science is designed to be self-correcting. That is the feature, not the bug.
The scientific method is iterative. A conclusion from one study becomes the observation that triggers the next question. Science is not a march toward final truth — it is a continuous process of getting closer to accurate descriptions of reality. This is important to say in an essay. Professors notice when students treat the scientific method as a procedure that produces certainties. It does not. It produces the best available explanations given the current evidence.
Falsifiability and Why It Matters
This is the concept that separates “science” from everything else. And it comes from one philosopher: Karl Popper.
Popper’s core argument, published in The Logic of Scientific Discovery (1934), is that a claim is scientific only if it is possible — in principle — to show it is wrong. A theory that can explain every possible outcome is not scientific. It is unfalsifiable. And unfalsifiable claims do not generate knowledge; they generate the appearance of knowledge.
Popper was bothered by the contrast between Einstein’s theory of relativity — which made precise, risky predictions that could have been proven wrong — and Freudian psychoanalysis and Marxist historical theory, which seemed to explain everything that happened after the fact. His criterion: a theory is scientific if it could, in principle, be refuted by an observation or experiment. “The sun will rise tomorrow” is falsifiable. “Everything happens for a reason” is not. This distinction — known as the demarcation problem — is central to any serious engagement with the question “what is science?” The Stanford Encyclopedia of Philosophy covers Popper’s demarcation criterion extensively and is a reliable source to cite in your essay.
Falsifiability is not the same as being wrong. A theory can be falsifiable and still be correct — it just means you have designed it in a way that it could be proven false if it were false. Einstein’s general theory of relativity predicted that gravity would bend light around massive objects. That was a falsifiable prediction. The 1919 solar eclipse observation confirmed it. Had the observation gone the other way, the theory would have required revision. That vulnerability is what made it scientific.
Falsifiable — Scientific
- “Smoking causes lung cancer” — could be tested and potentially disproven by epidemiological data
- “Objects fall at the same rate regardless of mass in a vacuum” — precisely testable
- “The MMR vaccine does not cause autism” — falsifiable; has been tested extensively
- “This drug reduces blood pressure” — a randomised controlled trial could show it does not
Unfalsifiable — Not Scientific
- “Everything is part of God’s plan” — no observation could contradict this
- “Crystals heal energy imbalances” — defined too vaguely to test
- “My theory is true but only detectable to those who believe” — immune to evidence
- “Bad things happen because of negative karma” — explains everything, predicts nothing
Science vs Pseudoscience
Pseudoscience uses the language and aesthetics of science — technical terms, charts, citations — without the method. It makes claims that resist testing, cherry-picks data, and often frames criticism as evidence of bias or conspiracy. Students are expected to know the difference.
Characteristics of Pseudoscience
Claims are vague or defined to avoid falsification. Evidence is anecdotal rather than controlled. The practitioner ignores or dismisses contradictory data. The claim has not been independently replicated. Criticism is attributed to the ignorance or malice of critics rather than addressed on its merits.
Characteristics of Science
Claims are specific and testable. Evidence comes from controlled, reproducible studies. Scientists update or abandon theories when data contradicts them. Findings are published in peer-reviewed literature and are open to independent replication. Critical scrutiny is welcomed, not deflected.
Examples of Pseudoscience
Astrology (claims cannot be precisely tested and fail when tested rigorously), homeopathy (contradicts basic chemistry and fails in placebo-controlled trials), and detox diets (the liver already does this; “toxin” is left undefined to avoid testing).
What Distinguishes Scientific Medicine
Randomised controlled trials. Double-blind design. Pre-registered hypotheses. Publication of negative results. Independent replication. Systematic reviews that aggregate evidence across multiple studies. The same treatment can fail these tests — that is what peer review is for.
Your essay will be stronger if you acknowledge that the line between science and non-science is genuinely contested. Popper’s falsifiability criterion is the most influential answer, but philosophers have criticised it — some legitimate scientific theories (string theory, for example) have not yet produced falsifiable predictions, and some pseudoscientific claims technically generate predictions that could be tested. Thomas Kuhn, Imre Lakatos, and Paul Feyerabend all offered competing accounts. Mention this. It shows you understand the question has depth.
Philosophy of Science — Key Thinkers to Know
If your assignment goes beyond introductory level, these names matter. Each represents a distinct answer to what science is and how it works.
Francis Bacon (1561–1626) — Knowledge Comes From Experience
Bacon is considered one of the fathers of the scientific method. He argued that reliable knowledge must come from systematic observation and inductive reasoning — not from authority or tradition. His work shifted European intellectual culture away from accepting Aristotle’s word as final and toward testing claims against reality. The key concept: induction — moving from specific observations to general principles.
Relevant for: Questions about the origins of the scientific method, empiricism vs rationalism, inductive vs deductive reasoning.Karl Popper (1902–1994) — Science Progresses by Ruling Things Out
Covered above. Popper’s key contribution is the demarcation criterion: science is science because it is falsifiable. His other major idea is that science does not prove things true — it eliminates things that are demonstrably false. All scientific theories are provisional. They survive until something better replaces them or until they fail a test they predicted they would pass.
Relevant for: The science vs pseudoscience distinction, the nature of scientific proof, falsifiability criterion.Thomas Kuhn (1922–1996) — Science Changes in Earthquakes, Not Trickles
Kuhn’s The Structure of Scientific Revolutions (1962) is one of the most cited academic books of the 20th century. His argument: science does not progress smoothly and incrementally. Most of the time, scientists work within an accepted framework (a “paradigm”) and patch around anomalies. When anomalies accumulate to a breaking point, the paradigm collapses and is replaced in a revolutionary shift. The shift from Newtonian to Einsteinian physics is the classic example.
Relevant for: How scientific knowledge changes over time, paradigm shifts, scientific revolutions vs normal science.Imre Lakatos (1922–1974) — Science Works in Programmes, Not Single Theories
Lakatos tried to fix Popper’s demarcation problem. Single experiments rarely kill a theory — scientists protect core assumptions by adjusting auxiliary hypotheses. Lakatos said what matters is whether a research programme is progressive (generating new predictions and discoveries) or degenerative (only explaining away problems after the fact). A degenerating programme is one sign that science is sliding toward pseudoscience.
Relevant for: More advanced philosophy of science essays, critique of Popper, how science actually behaves in practice.Core Characteristics of Science
If an assignment asks you to “describe the characteristics of science,” here is what to cover. Do not just list them — explain why each one matters.
Empiricism
Scientific knowledge is grounded in evidence from observation and experiment — not in authority, tradition, or pure reason alone. What you observe in reality is the final judge of a claim’s validity. If the data says your hypothesis is wrong, the hypothesis loses.
Objectivity
Science aims to eliminate personal bias from the process of knowledge generation. This is why experiments are designed with controls, why reviewers are anonymous, and why replication by independent researchers matters. No single scientist’s word is accepted as final. The method enforces objectivity structurally.
Reproducibility
A result that cannot be reproduced by other researchers is not reliable evidence. The replication crisis in psychology — where many famous findings failed to hold up when researchers tried to repeat the original studies — is a current live debate about whether the field meets this standard consistently.
Revisability
No scientific conclusion is immune to revision. New evidence can always update or overturn an accepted theory. This is not a weakness — it is precisely what makes science reliable. A system that updates based on evidence is more trustworthy than one that does not. “The science is settled” is a political phrase. In science, nothing is permanently settled.
Peer Review
Before findings are accepted by the scientific community, they go through expert scrutiny. Other scientists in the same field check for methodological errors, unsupported claims, and missing controls. Peer review is not perfect — biases exist, and some bad research gets through — but it is the best available mechanism for filtering reliable knowledge from unreliable claims.
Cumulative Knowledge
Science builds on itself. Each generation of scientists works from the validated findings of the previous one. This is why the pace of scientific discovery has accelerated — there is more to build on. It also means that errors, if they enter the literature, can propagate. Systematic reviews and meta-analyses exist partly to check for this.
How to Answer This in an Assignment
The question “what is science?” looks easy. It trips students up in predictable ways. Here is how to structure an answer that will satisfy a marker at introductory or intermediate level.
Open With a Definition — But Flag That It Is Contested
Give a working definition in your first paragraph. Something like: “Science is a systematic method for generating reliable empirical knowledge about the natural world through observation, hypothesis formation, testing, and evidence-based revision.” Then immediately note that the boundaries of science are debated — the demarcation problem has not been fully resolved. This shows you understand the question has depth without making your essay difficult to follow.
Address the Method, Not Just the Subject Matter
The subject matter of science changes. The method is the constant. An essay that focuses only on “science studies the physical world” misses the point. Biology, psychology, and economics are all sciences despite studying very different things — because they all use the same basic toolkit of hypothesis, testing, evidence, and revision. Make the method your central argument.
Include Falsifiability — It Is the Key Concept
Any substantive essay on “what is science?” needs to address Popper’s falsifiability criterion. You do not need to go deep into the philosophy — but you need to show you understand why testability matters and how it distinguishes scientific claims from non-scientific ones. One paragraph citing Popper and using a concrete example is enough at most levels.
Cover the Branches Without Just Listing Them
If your assignment asks for the major branches of science, do not just produce a list. Say something about how the methods differ across branches and why. Natural sciences rely more heavily on controlled experiments; social sciences often work with observational data because you cannot run double-blind trials on societies. Formal sciences use logical proof rather than empirical evidence. Those differences matter. Talk about them.
End With the Limits of Science — Not Just Its Powers
A sophisticated answer acknowledges what science cannot do. Science cannot tell you whether something is morally right. It cannot resolve questions that depend on values rather than facts. It cannot investigate claims that are outside the reach of observation and experiment. Ethics, aesthetics, metaphysics, and theology sit outside science’s domain — not because they are less important, but because the scientific method does not apply to them. Showing you know this boundary exists will distinguish your essay from the majority.
The Stanford Encyclopedia of Philosophy entry on “Philosophy of Science” (plato.stanford.edu) is peer-reviewed, freely accessible, and accepted as a credible source in most university contexts. It covers the demarcation problem, the scientific method, Popper, Kuhn, and Lakatos in detail. Use it for your citations. It is more authoritative than a general encyclopaedia and more appropriate than a textbook summary for a university-level essay on this topic.
What Students Get Wrong
Confusing Science With Technology
Science generates knowledge. Technology applies knowledge to build tools. Smartphones, vaccines, and bridges are products of technology — science provided the underlying knowledge. They are related but not the same thing. An essay that treats them as interchangeable is starting on the wrong foot.
Keep the Definition Focused on the Method
Science is the process, not the products. Anchoring your definition to empirical method, hypothesis testing, and falsifiability keeps you on solid ground and separates you from students who spend the whole essay talking about scientific achievements.
Treating Science as the Only Valid Form of Knowledge
Science is one way of knowing. History, philosophy, mathematics, law, and the arts are legitimate intellectual domains that do not use the scientific method — and do not need to. Claiming that non-scientific disciplines are therefore invalid will irritate most markers, especially in interdisciplinary programmes.
Situate Science Within a Broader Epistemology
Science is distinguished from other ways of knowing by its method — not by being superior in all respects. It is the most reliable tool we have for producing empirical knowledge about the natural world. For other kinds of questions, other tools are more appropriate. Making this distinction shows intellectual maturity.
Saying “Science Proves Things”
Science does not prove. It provides evidence that supports or contradicts hypotheses, with varying degrees of confidence. The language of proof belongs to mathematics and law. In science, even the most established theories — evolution, general relativity — are technically provisional. This is not a weakness; it is what makes science updateable and reliable over time.
Use the Language of Evidence and Probability
Write: “the evidence strongly supports,” “the data is consistent with,” “the current scientific consensus holds that.” These framings are accurate. They signal that you understand how scientific knowledge actually works, and they will read as more credible to any marker with a science background.
Ignoring the Philosophy Entirely
An introductory student can get away with a definition-plus-branches-plus-method essay. At intermediate or advanced level, skipping the philosophy of science — Popper, Kuhn, the demarcation problem — makes the essay thin. The question “what is science?” is partly a philosophical question. Address it as one.
Bring In at Least One Philosopher
Even one paragraph on Popper’s falsifiability criterion elevates the essay considerably. It shows you understand the question is contested and that you have engaged with the relevant intellectual tradition. Kuhn or Lakatos as a second reference signals genuine depth.
Frequently Asked Questions
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Before You Start Writing
Decide early what level of engagement your assignment requires. Introductory course: definition, branches, method, one example. Intermediate: add falsifiability, the demarcation problem, and at least one philosopher. Advanced: engage with Kuhn, Lakatos, the replication crisis, and the limits of science as an epistemological framework.
The thing most essays get wrong is treating this as a factual question with one correct answer. It is not. It is a conceptual question with a rich and ongoing debate behind it. Show that you know the debate exists. You do not have to resolve it — you have to demonstrate that you understand why it is unresolved.
And cite the Stanford Encyclopedia of Philosophy. It is free, it is peer-reviewed, and it is exactly the kind of source a university marker wants to see.
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