In general, observation yields facts and deduction yields theories. The appropriate balance of observation and deduction involves an appropriate relationship between fact and theory, Throughout the canon, I advocate time and again that theory should not outrace fact:

I have no data yet. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts [SCAN].

We approached the case, you remember, with an absolutely blank mind, which is always an advantage. We had formed no theories- We were simply there to observe and to draw inferences from our observations [CARD].

Now I make a point of never having any prejudices and of following docilely wherever fact may lead me --- [REIG].

It is a capital mistake to theorize in advance of the facts [SECO].

No data yet --- It is a capital mistake to theorize before you have all the evidence. It biases the judgment [STUD].

The temptation to form premature theories upon insufficient data is the bane of our profession [VALL].

Still, it is an error to argue in front of your data. You find yourself insensibly twisting them around to fit your theories [WIST].