I think what's you're saying is simultaneously technically correct and essentially silly.

Let's say I decide to go to my favorite restaurant for lunch. I don't *know* that I'll be able to get lunch there. Maybe last night everyone in the restaurant was shot dead in a horrible massacre and I don't know about it yet. Maybe it's burning down as we speak. Maybe it's under new ownership and the new owners will refuse me as a customer. Maybe my wallet's been stolen and I haven't noticed yet. Maybe someone has stolen my car and I can't actually get there. Maybe there's a sniper on the rooftop waiting to pick me off as I go for the car. Etc.

There are a lot of possibilities and a lot of things I don't know for sure, yet, it's generally silly to consider these things, and more sensible to go about my day as though I can in fact get lunch where I plan.

Evolutionary theory could be wrong on a lot of details. It could be completely invalidated in a year by the revealing of some grander truth. For all of that, it's got a good track record of predicting things we hadn't yet verified, and it makes sense -- until contrary evidence presents itself -- to speak in terms of what we know and move forward as though it's as good a predictor as it is, rather than attach 50 disclaimers to everything.

There's looking both ways before crossing the street, and then there's checking the radar to make sure a plane or missile isn't about to hit you before crossing the street. One is a sensible level of caution, and one just gets in the way of actually getting something done.