Gather Relevant Evidence, Including Evidence Against You

In the last chapter you saw that a claim needs grounds: the checkable evidence sitting under your recommendation. But grounds do not appear on their own, and the way you gather them quietly decides how good your claim can ever be. This chapter is about the gathering itself, finding evidence that actually bears on your decision, knowing where to look for it, and, above all, deliberately hunting for the evidence that might prove you wrong.

Start with What Makes Evidence Relevant

Before you gather anything, you need to know what you are gathering for. Not every true fact helps you, and a pile of true-but-beside-the-point facts can bury the decision instead of clarifying it.

Relevant evidence is information that bears directly on the specific recommendation you are weighing: it changes how good that particular choice looks. Everything else, however true or interesting, is noise for this decision.

Say you are deciding whether to switch your daily commute from driving to cycling. Your recommendation is “I should cycle to work instead of driving.” Relevant evidence is the stuff that actually moves that choice: how long the ride takes versus the drive, whether the route has safe bike lanes, what the weather is usually like at your commuting hours, and what each option costs you. Facts like “cycling is hugely popular in the Netherlands” or “my car is five years old” may be perfectly true, but neither one changes whether this commute, on these roads, is better by bike. They are not relevant here.

Know Where to Look

Once you know what counts as relevant, the next question is where to find it. You have two reliable wells to draw from, and between them they cover almost any everyday decision.

The first is public information: things anyone can look up without special access. For the commute, that means published route maps, an online journey planner, local weather records, and posted prices for fuel, parking, or a bike.

The second is your own everyday records: the small facts you can gather yourself just by paying attention. You could time your actual drive for a week, note what you really spend at the pump, or cycle the route once on a quiet day and see how it feels.

Here is a short way to picture the search before you start:

• Write the recommendation as one plain sentence, so you know what you are gathering for;

• List the public sources that speak to it: maps, prices, published records;

• List what you could record yourself: times, costs, a firsthand trial;

• Note, for each, whether you already have it or still need to go and get it.

Deliberately Look for Evidence Against You

Here is the move that separates a claim you can defend from one that only looks defended: you go looking for the evidence that could sink it.

Disconfirming evidence is information that would count against your recommendation, the reasons your instinct might be wrong. It is the most valuable evidence to gather and the easiest to skip, because we are all wired to notice what agrees with us and glide past what does not. That pull has a name, confirmation bias, and the cure is simple to state and hard to do: before you settle, deliberately ask “what would show that I am wrong?” and then go find out.

Back to the commute. You want to cycle, so your instinct hands you every reason it is a great idea. The disconfirming work is to hunt for the reasons it is not: the steep hill that leaves you sweaty before a meeting, the winter weeks when you would be riding home in the dark, the half-kilometer with no bike lane and heavy traffic. None of that is pleasant to collect when you have already fallen for the idea. All of it is exactly what makes your eventual claim trustworthy.

For two hard-nosed reasons. First, a recommendation that has survived your own best attempt to knock it down is far stronger than one you never tested, you can defend it precisely because you already tried to break it. Second, if you do not find the counter-evidence, the person you are trying to convince will, and it lands much worse coming from them. Finding it first also lets you improve the claim, maybe you scope it to “cycle from spring to autumn” instead of all year, which is a sturdier claim anyway.

Avoid Stacking the Evidence One Way

The failure this all guards against has a shape worth naming. One-sided evidence stacking is gathering only the pieces that point your way and quietly leaving out the ones that do not. The result feels overwhelming, every fact agrees with you, but it is overwhelming by design, not because the evidence really runs one way.

Gathering both ways does not mean you must end up with an equal number of points for and against, and it does not mean every decision is a toss-up. It means you looked honestly in both directions before you decided, so that whatever your evidence turns out to favor, it favors it for real. A short two-sided gather for the commute might look like this:

• For cycling: the ride is only eight minutes slower than the drive; it costs almost nothing; the route is mostly on quiet streets with bike lanes;

• Against cycling: one unavoidable stretch has no bike lane; the return trip is dark for about three winter months; there is a hill that makes summer mornings sweaty.

Notice that gathering the “against” list did not kill the idea, it sharpened it. With both columns in front of you, you can see a defensible claim taking shape (“cycle outside the dark winter months”) that you would have missed if you had only collected the cheerful half.

Let’s Recap!

• Relevant evidence is information that changes how good your specific recommendation looks; true-but-beside-the-point facts are noise for the decision at hand;

• Almost every everyday claim can be grounded in public information plus records you gather yourself, with no special access required;

• Confirmation bias makes you collect evidence that agrees with you, so you must deliberately seek disconfirming evidence by asking “what would show that I am wrong?”;

• Hunting for evidence against you makes the surviving claim stronger, spares you being ambushed later, and often improves the recommendation itself;

• One-sided evidence stacking can build a misleading claim entirely out of true facts, so gather honestly in both directions before you decide.

You now know how to gather relevant evidence on both sides of a decision. The next chapter shows you how to reason from that evidence to a conclusion you can actually stand behind, claiming only as much as the evidence really supports.