&gt;&quot;Is research into cancer drugs not science because we can&#x27;t predict beforehand if the drug will help a little or a lot, even though we know of the causal mechanism that should make the drug effective?&quot;<p>It is about the methods used rather than the level of understanding. Science is about people performing independent replications on each others measurements to ensure they are reliable and identify important confounds, then coming up with models that explain these reliable observations.<p>The issue with cancer research right now appears to be it is common to not even publish enough info to do the replications, let alone actually perform them. Once we had some data to &quot;hang our hat on&quot;, then it would be time to try to explain this quantitatively. If you can&#x27;t predict whether a drug will help a little or a lot, I am extremely doubtful the causal mechanism is known.