逻辑学 names the academic field (formal logic, mathematical logic, dialectical logic). For 'logical thinking' as a quality of an argument, use 逻辑 alone (这没有逻辑 'this has no logic'). Add 学 only when referring to the discipline itself.
memory
逻辑 is itself a 20th-century phonetic loan from English 'logic' - not a native compound. Adding 学 (study of) turns it into the discipline. Compare 经济学 economics, 心理学 psychology - same pattern.
