 Although the cognitive role of analogy is central, it relies on subjective judgment and so it can have idiosyncratic manifestations. Things are similar in an infinite number of ways, and only some of these similarities can be exploited with the hope of cognitive benefit (THN 1.1.5.3). As any thing may resemble any other in an infinite number of ways only some resemblances can explain associative relations between ideas. Resemblances of cognitive relevance are therefore not passively detected, but they are actively produced by memory: we remember past instances as resembling (THN 1.4.6.18). Depending on the resemblances one recognizes among particular instances, one can end up with different and potentially conflicting conclusions concerning the causes of phenomena. Therefore, as Hume puts it: