The following quote, often attributed to Einstein, is a gem:

Not everything that can be counted counts, and not everything that counts can be counted.

However, QuoteInvestigator points out that it is likely due to the sociologist William Bruce Cameron, who wrote the following in his 1963 text Informal Sociology: A Casual Introduction to Sociological Thinking.

It would be nice if all of the data which sociologists require could be enumerated because then we could run them through IBM machines and draw charts as the economists do. However, not everything that can be counted counts, and not everything that counts can be counted.