That which the scientists considered certain would be rendered uncertain. Second, the senses can and frequently do deceive us. Anyone who has ever shoved a straight stick into a body a water and noticed that it appears to bend can attest to this. Fourth, one can never have the same experience twice. The ancient philosopher Heraclitus pointed this out centuries ago when he stated that no one ever stands in the same river twice.
Finite things continue to change, even as the water in the river continues to flow.
In such a system, verification is not possible. In fact, the basic axiom of empiricism, namely that truth can only be attained by means of verification or falsification by scientific investigation, itself cannot be verified. Thus, empiricism is founded on a fallacious starting point. Sensation might inform us that doors have two sides, but it cannot teach us that all doors must have two sides. No experience can disprove the idea that some doors might have one side.