Literally: think – consider – part – separate
Alternately: Making judgments based on careful consideration. Thinking deeply about the merits of a situation and only then deciding.
Notes: Again we have two two-character words of related meaning compounded into a single phrase for emphasis. 思慮 is careful thought, and 分別 is distinguishing truth from fiction or right from wrong.
A close synonym replaces 思 with 熟 (juku), “ripen.” Note that 分 is pronounced fun rather than bun; there exists a homonym 分別 (bunbetsu), “separating” (out different categories of things) or “classification.”