The specific problem he was facing was looking a DNA polymerases - and the problem with enzymes is they are catalytic - so a 1% impurity at the protein level might account for 100% of the activity you are measuring and wrongly ascribing to the 99% of purified protein.
So much of science is trying not to fool yourself.
'don't waste clean thought on a dirty enzyme'
The specific problem he was facing was looking a DNA polymerases - and the problem with enzymes is they are catalytic - so a 1% impurity at the protein level might account for 100% of the activity you are measuring and wrongly ascribing to the 99% of purified protein.
So much of science is trying not to fool yourself.