   Lastly, one might argue for simples as the basis of an empirical argument; i.e., one might claim to have completed the process of analysis and to have reduced all sorts of truths down to certain entities that can be known in some way or another to be simple. Russell is sometimes interpreted as having reasoned in this way. According to Russell’s well known “principle of acquaintance” in epistemology, in order to understand a proposition, one must be acquainted with the meaning of every simple symbol making it up (see, e.g., KAKD, 159).  Russell at times suggested that we are only directly acquainted with sense data, and their properties and relations, and perhaps with our own selves (KAKD, 154ff). It might be thought that these entities are simple, and must constitute the terminus of analysis. However, Russell was explicit that sense data can themselves be complex, and that he knew of no reason to suppose that we cannot be acquainted with a complex without being aware that it is complex and without being acquainted with its constituents (KAKD, 153; cf. TK, 120). Moreover, Russell continued to use the label “logical atomism” to describe his philosophy long after his epistemology had ceased to center around the acquaintance relation. (For further argumentation on these points, see Elkind 2018.) Indeed, Russell eventually came to the conclusion that nothing can ever be known to be simple (MPD, 123).