Whenever you see a tweet, social media posting, or any other statement which starts with the words scientific fact, you can pretty well guarantee that what follows has nothing to do with any science, and, far from being proven fact, is personal opinion which defies any evidence.

This unwitting irony is becoming as common as the use of the word literally to mean in any sense but the literal, a phenomenon regularly explored on Language Log and elsewhere.

The most recent example which reminded me of this new rhetorical trope reads: “Scientific fact-disease is caused by negative energy. Is it possible your ill health is caused by your negative attitude?” (Twitter, @NoelEdmonds to @VaunEarl, 08:00 07/06/2016.) Several have already commented that they were not aware of a fact-disease, but I am prepared to put that down to character limits rather than pick that nit. Clearly its author’s intention was to claim that the statement disease is caused by negative energy is a ‘scientific fact’.

A quick rummage around Twitter reveals many other recent examples of this phrase:

• total scientific fact, your brain doesn’t work as well when you’re sick ’cause when you’re dehydrated which
• People with higher cholesterol levels actually live longer, and that is a scientific fact
• Midtown hueys just put a trivia question about the abominable snowman under the category “mythology” when it is obviously scientific fact
• Human life begins at the point of conception, this is a scientific fact, inconvenient – but true.
• Oh, it’s an established scientific fact that all illness stems from negativity. If only people could feel happy, then nobody would ever die.
• FYI, Squirrels are one of the SMARTEST animals in the world. That’s a scientific fact.
• Scientific fact•(smart) Lazy ppl accomplish more. Their laziness actually enables them to find the easiest/quickest ways to get things done.
• Except it’s already scientific fact that those of European descent have Neanderthal genes as well. NOT FROM AFRICA.
• oh men are more emotional lol this is a proven scientific fact. Women are just allowed to be more emotional due to social construct
• Now that is scientific fact. There’s no real evidence for it – but it is scientific fact.

Popular topics in which people assert such ‘scientific facts’ include evolution, gender, climate change, and fracking. It appears that people seldom claim that non-controversial statements, which could be readily tested in a simple way, are ‘scientific facts’. It often seems to be used to bolster an opinion which could not be supported by a simple fact in the first place, and one which is reliant on a particular interpretation of evidence which the author is not familiar with anyway.

The phrase also occurs in plain irony and humour:

• People named Josh are just funny. It’s a scientific fact.
• It is a scientific fact that your body will not absorb cholesterol if you take it from another person’s plate or If its FREE……;))
• it’s like a scientific fact that every kid has to own a goldfish at some point

Unfortunately, and despite many good techniques of making irony clear in language, the availability of punctuation, and emojis, most authors leave the reader to guess whether there is intentional irony, rather than signalling that to the reader.

The concept of a scientific fact is, in any case, a profound irony. Over the last 50 years and more, the sciences have appreciated that, in science, there are remarkably few statements which are invariably incontrovertible, and can thus be treated as facts. The overwhelming majority of statements which arise from science are hypotheses and theories, which serve as working models until such time as they are superceded by better.

Particularly in the biological sciences, and most of all in humans, almost everything ‘known’ is subject to probability, too. Even when you think that you have reached a fairly clear conclusion, that needs to be moderated by the estimated chance of that conclusion being valid. So the scientific fact is that any scientific fact is only an interim working hypothesis, which already has a significant chance of being wrong.