Welcome back to "Doggerel," where I ramble on about words and phrases that are misused, abused, or just plain meaningless.
This particular doggerel was once spouted by an old troll named John Best. It demonstrates just how poorly he grasps science. "Probably" is what science is based on. Certainty is only for religious fanatics and mathematicians. Only the latter have a legitimate claim. Whenever you conduct an experiment, you have to keep open to the possibility something unknown is influencing the results, that factors outside the lab might produce exceptions, and so forth. I can drop apples all day to measure the effects of gravity and derive various laws and principles from the act, but there may very well be some sort of undiscovered anti-gravity phenomenon somewhere out there in deep space. That's speculation right now, but with any scientific knowledge, any new discoveries can change our understanding of the universe.
Additionally, with repeated experiments, especially "noisy" ones like medicine, statistical analysis becomes paramount. If you're trying to see if a chemical causes a response, you can't just try it on one person or cell culture and say it's so. You have to try it on multiple subjects and see if it's different from those not affected by it. That's what double-blind control studies are about. There has to be a statistically significant difference between the two groups. If you find one big enough to pass that bar, you haven't proven without a doubt that it has an effect, just that there's a very big chance it does. That's what the "p-value" is about: The chance that the effects could have been attributable to random chance. There's a chance if you repeat the experiment, you might find you just got lucky. It's unlikely but possible. That's one more reason why experiments are supposed to be replicable: Each successful replication makes it more unlikely to be chance.
Science is all about "probably." No matter how thinly you slice it, you can't arrive at perfect knowledge without being omniscient in the first place. Woos may love to depict that as a weakness of science, but it's not. Science is always open to change and growth. Those who claim to have certainty, especially if they maintain lower standards than science demands, are closing their minds.