You think that the woman you regard as your mother gave birth to you. But it’s an open question; there’s still debate, and it’s definitely not an open and shut case. Right?

Is she really?

No, no, I’m not being silly. I mean it. You need to prove to me that she’s your mother. You’ve got a birth certificate? Just a bit of paper. You look like her? Coincidence. DNA test? Useful, but not 100% accurate. She’ll swear that it’s true? Well, she might be lying, or was duped at the hospital. A photo of her holding you as a baby? Doctored. You don’t have a leg to stand on!

In the absence of conclusive evidence that she’s your mother, you should suspend contact immediately, examine the evidence more carefully and make a decision about whether you continue the relationship at a later date. By investing in a relationship with your supposed ‘mother’ now, you’re wasting time and energy that could be better spent earning money or having fun.

Kudos to those who’ve guessed where I’m going with this! I’m trying to make a point about the way we know things.

None of our knowledge about the world can be viewed as certain, or settled. Even something as fundamental as the identity of our biological family is hard to be certain about. That’s because all of our knowledge is incomplete. Whether it be the next song on my iTunes playlist, the exact time the train will arrive at the tube stop tomorrow morning, or whether climate change is a real problem, I just can’t be certain.

“Wait a minute, David,” you say. “I thought you were pro-science and pro-evidence. If all knowledge is incomplete, how can we be expected to make decisions about things? We could be wrong and then it would have been a waste!”

Good question, rhetorical reader! Of course, we make decisions based on incomplete information all the time. We also take things to be true even if they’re not totally and exhaustively backed up by evidence. To live any other way would be a waking nightmare of fact-checking and second-guessing. It doesn’t matter if we apply science or common sense or any other way of assessing information that we choose: there will always be uncertainty.

I’m not sure if I’m going to get stolen from, but I have insurance for my camera gear. I’m not sure if I can make a career in science communication, but I’ve invested 3 years of hard-earned savings into the course I’m doing. I’m not completely sure if my mother really gave birth to me, but I still Skype her each week! Why? Because evidence can be weighed and assessed. Questions about the world are not, fundamentally, yes or no questions. If we’re completely honest, those answers are only useful as approximations of our certainty about the situation.

This might all seem trivial and obvious, but it’s important. A recurring ploy in the media is the manufacturing of uncertainty by vested interests, and the manipulation of doubt and the nature of truth is at the heart of the matter. Forcing someone into a yes or no answer to a question is an extremely effective way of getting them to misrepresent their own opinion. This scenario has played out repeatedly with climate scientists in the past few years. It’s nice, then, to see someone avoid the trap! Check out this interview with environmentalist Ed Begley, Jr. getting into a shouting match with a right-wing commentator.

Begley Jr. wrests control of the interview away from the interviewer, and while it’s not ‘pretty’ interview technique, it was certainly much more effective than calmly trying to discuss why ‘settled’ isn’t appropriate in the context.

Don’t fall into the trap of equating uncertain with ‘right’ or ‘wrong’: uncertainty is always going to be a part of science and the world around us. Understand that, and when you hear anyone – no matter who they are – invoke words like ‘may show’ or ‘calls into doubt’, take their words with a grain of salt. On the flipside, if you see someone trying to eliminate uncertainty from a proposition, they’ve probably got an agenda to push. What is important is the amount and quality of evidence supporting the proposition.

Uncertainty dominates our lives, but it’s also a powerful rhetorical device and should be given healthy respect as such!