This document discusses issues related to contrastive analysis (CA) between languages. It addresses two main sources of insecurity for CA: 1) Criteria for comparison between languages and 2) whether languages are truly comparable. Regarding criteria, it examines using surface structure, deep structure, and translation equivalence as potential common bases for comparison. However, each approach has advantages and disadvantages. Determining an appropriate universal criterion that captures similarities while also allowing for differences between language systems has proven difficult.