Natural Sciences

Scope

Sean Coleman

2026-04-28

When you picture a scientist…

• A slightly crazy mad professor?
• Working alone in a lab?
• Surrounded by sophisticated (possibly dangerous) equipment?
• Almost certainly a man?

Why is this image so deeply embedded in public consciousness?

Open with the image — draw it out of students first, don’t just tell them. Ask who thinks of this. Then ask: Why is it a man? Why alone? Why slightly unhinged? The point is that the stereotype tells us something about how science is perceived — but almost nothing about what it is. Bridge: “Today we go looking for a better answer.”

Today’s questions

1. Is there something special about the natural sciences?
2. What is the difference between pure and applied science?
3. How do we tell science from pseudoscience?

Roadmap slide — keep it brief, 30 seconds max.

Unit Knowledge Question

“Is there solid justification for regarding knowledge in the natural sciences more highly than knowledge in another area of knowledge?”

What Makes a Natural Science?

The Central Question

Is there something special about the natural sciences that marks them out from other areas of knowledge?

In ToK we look for a necessary and sufficient condition —

a feature that all natural sciences share and that no other AoK shares.

(We should always be prepared to find that no such feature exists.)

Introduce N&S conditions briefly — this is a useful ToK concept they’ll use all year. A necessary condition is one that must be present; a sufficient condition is one that, if present, guarantees the result. An N&S condition does both.

Candidate 1: The Method?

Natural sciences involve:

• Systematic observation and measurement
• Controlled experiments
• Mathematical analysis of results
• Model and theory construction
• Predictions about future events

Problem: other AoKs do these things too.

Psychology runs experiments. Economics uses mathematical models. Neither is normally considered a natural science.

This is a genuine puzzle — the method alone doesn’t carve out the natural sciences. Let the students feel the problem before moving on.

Candidate 2: The Subject Matter ✓

The natural sciences study the natural world bereft of human interference.

Their subject matter would exist even if humans did not.

Natural sciences

• Hydrogen is the lightest element
• The sun will shine after we’re gone
• These are true with or without us

Human sciences / History / Arts

• These disappear if you remove human beings from the picture

This is the key move: the criterion is subject matter, not method. Useful to contrast with economics and psychology — they use the same methods but study human behaviour, which is not “natural” in the relevant sense.

Objectivity — and the Problem

Scientists are human. They have biases, intentions, cultures.

So how can science tell a story about the world independent of these things?

Answer: through method.

The scientific method is designed to cancel out the human component:

• Results must be replicable — same result whoever does the experiment, wherever
• It doesn’t matter who does the experiment or what socks they’re wearing
• This produces brute facts — true regardless of religion, culture, gender, politics

“Water is H₂O” is a brute fact.

The tension: we want science to be objective, but it’s produced by human beings. The method is the answer to this tension — not a perfect answer, but the best we have. Brute fact: contrast with “social facts” like money or marriage, which depend on human practices.

Complete Objectivity: Ideal or Reality?

Complete objectivity may be more of an ideal than a reality.

We may find that the gap between the Natural Sciences and other AoKs is smaller than we first thought.

(More on this in Methods and Tools…)

Don’t linger here — plant the seed of doubt and move on. The point is that science aims at objectivity and its methods are the best we have, not that it achieves perfect objectivity.

The Aim: Natural Explanations

“Science is a way of looking for natural explanations for all phenomena.” — Michael Shermer

Term	Meaning
	A puzzling event to be explained
	What it is, how it’s caused, or both
	Only draws on matter and forces — no supernatural elements

Example: Lightning is a phenomenon. The explanation (electrostatic discharge between cloud and ground) is a natural explanation.

Quick-fire definitions — check comprehension with the lightning example. “What’s the phenomenon?” → the flash / the event. “What’s the natural explanation?” → electrostatic discharge, charge buildup from air particle movement. “What would a non-natural explanation look like?” → Zeus / divine wrath.

The Disciplines

Four main areas, each studying a different aspect of the natural world:

Discipline	Examples
Physics	Cosmology, particle physics, condensed matter
Chemistry	Organic, biochemistry, inorganic, analytical
Biology	Genetics, ecology, evolutionary biology
Earth Sciences	Geology, seismology, meteorology

One thing (e.g., water) can be studied by all four — but the phenomena they investigate are different.

Use the water example: chemistry studies H₂O composition; biology studies water’s role in the cell; physics studies flow; earth sciences study the hydrological cycle. Same “thing,” different phenomena.

Discussion Question 1 (pairs · 2 min)

“Is it possible to have a science of something that depends on human beings?”

Think of psychology or economics. Are they natural sciences? Why or why not?

Students should surface the subject-matter criterion themselves here. Listen for: “psychology studies human behaviour,” “economics depends on human decisions.” If someone argues psychology is a natural science (the brain is physical), that’s a great tension to hold — bring it to the class.

Pure and Applied Science

Two Directions of Scientific Work

	Pure Science	Applied Science
Motivation	Curiosity — knowledge for its own sake	Solve a practical problem
Product	General models and theories	Working technology
Scale	As general as possible	Accounts for local variables
Direction of fit	Knowledge must fit the world	The world must fit the specification

“Direction of fit” is the key philosophical idea here. It’s borrowed from speech act theory (Searle) but works perfectly for this distinction. Pure scientist: “My theory must match reality — I change my theory when the world says otherwise.” Applied scientist: “The world (or the Skytrain) must match my specification — I change the world.”

The Bangkok Skytrain Example

Pure science: A physicist studies the general physics of lightning — the theory applies anywhere on Earth.

Applied science: An engineer must protect the Bangkok Skytrain from lightning strikes.

The engineer must:

1. Apply the general theory
2. Account for messy local variables (Bangkok’s weather, the specific equipment)
3. Change the world to match a safe specification

The pure scientist changes their knowledge to fit the world. The applied scientist changes the world to fit their knowledge.

Concrete and vivid. Students often remember this example well. Emphasise that the engineer uses the pure scientist’s theory — it’s not that applied science is better, they need each other.

Case Study: Grindavik, Iceland (2023–24)

• Autumn 2023: Seismologists detect hundreds of micro-tremors near the town of Grindavik
• Modelling suggests a magma lake is forming underground
• Recommendation: evacuate the town
• 18 Dec 2023: eruption begins
• 14 Jan 2024: second fissure, closer to town; second evacuation
• Result: no lives lost

Iceland sits on the Mid-Atlantic Ridge — the North American and Eurasian plates pulling apart.

Seismology is pure and applied — it cannot be neatly separated.

Key insight: seismology cannot tell you when an eruption will happen — only that risk is high. Yet that probabilistic knowledge still saved lives. This is risk assessment without precise predictive power — a powerful idea for TOK. Ask students: “Is this a success or a failure of science?”

The Key Insight from Grindavik

An applied science can have a profound effect on human life through risk assessment — even without precise predictive power.

Science doesn’t always give us certainty.

Sometimes probability is enough — and that itself is worth knowing.

This sets up a great discussion about what we want from science. Do we need certainty? Or is well-grounded probability sufficient?

A Historical Footnote

The word “scientist” was invented in the 19th century by English polymath William Whewell (who also coined cathode, anode, and ion).

Before this: all knowledge was scientia — Latin for “knowledge” of any kind.

The idea that science is fundamentally different from other knowledge is a surprisingly recent cultural development.

This is a great unsettler — students assume the science/non-science distinction is obvious and ancient. It isn’t. Note that Whewell invented the term in response to a challenge from the poet Samuel Taylor Coleridge. Science and poetry were in dialogue at the birth of the concept.

Discussion Question 2

“Should we value pure science (curiosity-driven) even when it has no obvious practical application?”

Who should fund it — and why?

If students say “only fund what’s useful,” push back: CERN/particle physics seemed useless — then gave us the World Wide Web (Tim Berners-Lee) and PET/MRI scanners. Can we ever know in advance what will be useful? If students say “fund everything,” push back: resources are finite. How do we allocate?

Science, Non-Science, and Nonsense

Three Categories

Category	What it is	Example
Science	Systematic, testable knowledge of the objective world	Physics, chemistry, biology
Non-science	Perfectly good knowledge — just not about the objective world	Arts, history, human sciences
Pseudoscience	Looks like science but claims cannot be properly tested	Astrology, homoeopathy

Key move: Non-science is not lesser knowledge. It’s just different knowledge.

The problem is pseudoscience — which is not knowledge at all.

Students sometimes think “non-science = bad.” Correct this immediately. A historian or a musician produces real knowledge — just a different kind. The dangerous category is pseudoscience.

What Makes Knowledge Real?

In every genuine area of knowledge, researchers can (and do) get things wrong:

• Art experts can misidentify paintings
• Historians can misinterpret primary sources
• Economists can fail to predict recessions

The ability to be wrong is a hallmark of genuine knowledge.

You can only be wrong if there is a fact of the matter to be wrong about.

This is a deep point. If a system cannot be wrong, it isn’t tracking reality — it’s just a closed story. Real knowledge is vulnerable to the world pushing back on it.

Pseudoscience: Being Wrong Is Not an Option

Astrology — using the stars to predict human lives:

• Predictions are so vague they fit any event
• Stars in a constellation are at vastly different distances from Earth — no physical mechanism connects them
• Regulus (brightest star in Leo) is ~79 light years away
• To influence tomorrow, it would have had to ‘act’ just after World War II

The 79 light-year point is great for students who do physics — information/causal influence cannot travel faster than light. So any influence from Regulus on your day tomorrow would have left the star in ~1947. Ask: “Does that seem plausible?”

Pseudoscience: Homoeopathy

Homoeopathy — water “remembers” a diluted substance and cures disease:

• Dilution so extreme that no active chemical remains
• When tested rigorously, supposed benefits disappear
• When a rigorous test is proposed, proponents argue the test interferes with the medicine

This last move creates a closed explanation.

The homeopathy example resonates with students who may have encountered it. The “memory of water” claim is worth unpacking briefly — at the dilutions typically used, there is statistically not even one molecule of the original substance left.

The Closed Explanation

A closed explanation rules out the possibility of itself being wrong.

Example: Uri Geller claimed to bend spoons with his mind.

Under controlled scientific testing, he claimed the scientists’ negative energies prevented a successful outcome.

This is like saying: “Only examiners who will give me a 7 are qualified to mark my essay.”

This lands well with IB students — they immediately see the absurdity. A closed explanation is unfalsifiable by design. It’s a self-sealing belief system. Ask: can you think of other examples of closed explanations?

Karl Popper and Falsifiability

Karl Popper (Austrian philosopher of science):

For a knowledge claim to be scientific, it must be possible to show that it is false.

• A claim that can never be wrong is not scientific
• The ability to be tested and potentially refuted is what makes science science

Not the same as saying it is false — just that it could be, in principle.

Popper is a key figure for TOK — worth spending 30 seconds on who he is. Austrian philosopher, developed falsifiability partly in reaction to the unfalsifiable nature of Freudian psychoanalysis and Marxist historical theory, which he saw as “explaining everything” and therefore nothing.

Seven Criteria: Science vs. Pseudoscience

Criterion	Science	Pseudoscience
Replicable	Same results when repeated by competent scientists	Results NOT reproducible
Consistent	Claims do not contradict each other	Claims may contradict
Observable	Evidence observable with senses or instruments	Evidence NOT observable
Natural	Uses natural causes / mechanisms	Does NOT use natural causes
Predictable	Accurate predictions from natural causes	Predictions NOT based on natural causes
Testable	Controlled experiments are possible	Experiments CANNOT be designed
Tentative	Explanations change with new evidence	Explanations do NOT change

Give students a moment to scan this table. Then ask: “Which of these criteria do you think is most important? Which is hardest to satisfy?” Key caveat coming up on next slide: many of these also apply to other AoKs.

The Caveat

Many of these features also appear in other areas of knowledge.

• History aims to be consistent and testable (by evidence)
• The human sciences aim to be tentative and open to revision
• The arts involve observable works that experts can evaluate

We may not find criteria that are uniquely and exclusively scientific.

That itself is a ToK insight.

Don’t let students walk away thinking the seven criteria neatly separate science from everything else. The point is that the criteria form a cluster — science satisfies all of them robustly; pseudoscience fails most of them.

Case Study: Alchemy

Alchemy tried to transmute lead into gold, rooted in:

• Aristotelian four elements (air, earth, fire, water)
• A complex spiritual worldview (gold = perfect; lead = sinful)

In the 17th century, there was little to separate alchemy from early chemistry.

• Isaac Newton was an alchemist
• Galileo wrote astrological predictions

It took the conceptual revolution of 18th-century chemistry and the periodic table (early 19th century) to definitively end alchemy.

Some alchemical practices were absorbed into modern chemistry.

This is the destabiliser — Newton! If the greatest scientist who ever lived was an alchemist, what does that tell us about the science/pseudoscience boundary? The answer: it’s historically contingent. The boundary is not fixed. It shifts as knowledge develops.

The Uncomfortable Conclusion

The relation between science and pseudoscience is complex and not as clear-cut as it first seems.

In 200 years, which of today’s beliefs might look like alchemy?

Let this land. Don’t answer it — it’s a genuinely open question.

Discussion Question 3 (pairs · 2 min)

Think of a claim you’ve seen in advertising or on social media.

Apply the seven criteria. Is it science, non-science, or pseudoscience?

Good examples students bring up: anti-ageing creams, detox diets, “clean eating,” astrology apps, supplement claims, certain wellness influencers. Listen for: which criteria does it fail? Is it testable? Is it tentative?

Discussion Questions

Choose 2–3 based on your class. Allow 2–3 min per question with probing follow-ups.

You don’t need to use all five — pick the ones that seem most alive in your room based on what’s come up so far. The questions build in difficulty: A is definitional, B is epistemological, C is political, D is sociological, E is the deepest.

Question A — Defining Science

“Is there a single defining feature that makes something a natural science?

Or is ‘natural science’ more like a family resemblance — a cluster of overlapping features with no single necessary and sufficient condition?”

Follow-up: What would John Dupré say? Do you agree?

Dupré (2001) argues there is no single feature that marks out the natural sciences — that “science” is not a natural kind. Students who argue for a defining feature should be pressed: can they state it precisely? Does it include all the sciences and exclude everything else?

Question B — Objectivity

“Can science ever be truly objective?

Or is complete objectivity an ideal that can never fully be achieved?”

Follow-up: Does the fact that scientists are human undermine the objectivity of science — or is that exactly what the scientific method is designed to prevent?

Good tension: the methods are designed to cancel the human factor, but the methods themselves are designed by humans. Can you ever escape the human element entirely? The sociology of science (Kuhn, Latour) argues no — paradigms, funding, culture all shape science.

Question C — Pure vs. Applied

“A government must allocate limited research funding.

Should it prioritise blue-sky pure research (unknown practical value) or targeted applied research (concrete benefit to citizens)?”

Follow-up: Particle physics seemed useless for decades — then gave us the World Wide Web (CERN) and PET/MRI scanners. Does this change your answer?

The practical argument for pure science: you can’t know in advance what will be useful. The practical argument against: resources are finite and people are dying of diseases now. Ask: who should decide — scientists, politicians, the public?

Question D — Policing Pseudoscience

“Pseudoscience can be dangerous — anti-vaccine movements, homoeopathy replacing medicine.

But is it the job of science to police the boundary between science and pseudoscience? Who should decide?”

Follow-up: Could a scientist’s confidence in their own method itself become a kind of closed explanation? Is scientism a risk?

Scientism = the view that science is the only valid form of knowledge. This is itself a philosophical claim, not a scientific one. Can science validate itself? This is a deep problem of self-reference. The practical question: if not scientists, who should police pseudoscience? Governments? Courts? Individuals? Each has problems.

Question E — The Alchemy Problem

“If Newton was an alchemist and Galileo wrote horoscopes, does this mean the boundary between science and pseudoscience is historically contingent?

What does this tell us about scientific claims made today?”

Follow-up: In 200 years, which of today’s beliefs might look like alchemy?

This is the deepest question — it concerns the reliability of the method over time, not just at a moment. Students who reach the idea that today’s science might be tomorrow’s alchemy have grasped something genuinely profound about the nature of knowledge. This is where TOK lives.

Conclusion

Three Things to Leave With

1. Subject matter: The natural sciences study the natural world as it exists independent of human beings — that is what makes them natural sciences.

2. Method: The scientific method is designed to cancel out the human factor and produce objective knowledge — though complete objectivity remains an ideal.

3. The boundary: The line between science, non-science, and pseudoscience matters — but is not perfectly sharp. Non-science is not lesser knowledge; pseudoscience is not knowledge at all. The key tests are testability and falsifiability.

Walk through these slowly. One sentence each. Then go straight to the exit ticket.

Exit Ticket

Write 2–3 sentences — choose one:

Option 1: “In your own words: what makes something a natural science rather than a pseudoscience?”

Option 2: “Give one example from your own science class. Is it pure or applied science? Explain the direction of fit.”

Option 3: “Name one claim you have encountered that might be pseudoscientific. Which of the seven criteria does it fail?”

Give 2 full minutes for this. Collect on your way out or as a quick show of hands (“who picked option 1?”).

Reference

Key Terms

Term	Definition
	A puzzling event or situation to be explained
	Draws only on matter and forces — not supernatural
	A fact independent of any perspective or observer
	Knowledge independent of human values or desires
	Knowledge-production for its own sake; curiosity-driven
	Using scientific knowledge to solve practical problems
	Pure: knowledge fits the world. Applied: world fits the specification
	Claims that look scientific but cannot be properly tested
	An explanation that rules out the possibility of itself being wrong
	Popper’s criterion: a claim must be capable of being shown false
	Perfectly good knowledge of things inherently human (arts, history)

TOK Connections

• Knowledge and the Knower — Can an individual scientist be objective?
• Knowledge and Language — How does the word ‘science’ shape what counts as knowledge?
• Methods and Tools — How does the scientific method produce reliable knowledge?
• Ethics — Who is responsible for how applied science is used?
• Human Sciences AoK — Where does psychology sit relative to natural science?
• History AoK — How do we know about the history of science (e.g., alchemy)?
• Core Theme: Knowledge & Responsibility — Who should fund and direct scientific research?

Schedule