麻豆传媒

NULLIUS in verba: 鈥渢ake nobody鈥檚 word for it鈥�. The motto of the Royal Society, the UK鈥檚 national academy of science, encapsulates the spirit of scientific enquiry. Do an experiment, record its outcome faithfully and objectively, and make that record available for doubters.

This way of working means that, if knowledge is defined as the route to the truth (see 鈥�Knowledge: What separates fact from belief鈥�), science is an expressway to enlightenment. Thanks to what science tells us about human physiology, the universe鈥檚 history, nature鈥檚 forces and Earth鈥檚 geology, flora and fauna, we know Earth isn鈥檛 flat, the universe is nearly 14 billion years old, and that there are no dragons or unicorns. We live longer and in more comfort, and can send space probes to the edge of the solar system. Pretty darn special, huh?

Inside knowledge: The biggest questions about facts, truth, lies and belief

Forget alternative facts. To get to the bottom of what we know and how we know we know it, delve into our special report on epistemology 鈥� the science of knowledge itself

But let鈥檚 take a more sceptical look, starting with that 鈥渨e鈥�. Some people do believe Earth is flat. Others say the universe is 6000 years old. Some doubt the theory of evolution by natural selection, or the reality of human-made climate change. We is not everyone.

Unicorns in loch ness

It is tempting to say that鈥檚 their problem, not science鈥檚. But science is also limited in what it can say. It can鈥檛 prove a negative: there might be dragons and unicorns, a monster in Loch Ness, a God. It can鈥檛 even be definitive about all the positives. 鈥淥ur evidence may at times leave us able to make only probabilistic judgements 鈥� we may sometimes be restricted to saying that a certain outcome or theory is likely to be true,鈥� says Jennifer Nagel at the University of Toronto, Canada.

This weakness becomes greater as we extend the scientific method into more complex realms with more variables and so more uncertainty, such as social science or climate change. Science progresses legitimately through speculation and hypothesising, but until these speculations are tested by experiment, for a stickler any 鈥渒nowledge鈥� that emerges from them must strictly be labelled as provisional.

It is a weakness (or strength, depending on your point of view) exploited with gusto by climate-change sceptics, among others. But it points to a blunt truth: if scientific knowledge feels special to you, you are in its in-group. As we grow up, we absorb beliefs from our cultural environment. For some that means accepting scientific knowledge; for others it means 鈥渞evealed鈥� knowledge, from the Bible, say.

And here鈥檚 the thing. For all the bluster about 鈥渢he evidence鈥�, if you are a scientific believer you too are taking almost all of it on trust. 鈥淚n principle everybody should be able to replicate scientific results given time, money and training,鈥� says at the University of Nottingham, UK. 鈥淏ut not everyone has a Large Hadron Collider or a climate-modelling computer.鈥� You are taking someone鈥檚 word for it. Like other forms of knowledge, most of science comes down to trusting the source.

Not special, then? Perhaps 鈥� except that science also provides mechanisms to justify trust in the knowledge it generates. 鈥淎uthority in science is earned 鈥� at least, when a scientific community is functioning well 鈥� by success at predicting, and more generally at analysing, empirical phenomena,鈥� says philosopher of Harvard University. Science鈥檚 conclusions are accepted when they fit with our experience of the physical world, and are discarded when they cease to. That makes trust in science a justified true belief 鈥� and knowledge that true science generates a cut above the rest. Just don鈥檛 take my word for it.

This article appeared in print under the headline 鈥淚s scientific knowledge special?鈥�