For a pure disposition is a fictitious entity. The expressions that ostensibly denote dispo- sitions are best construed as syncategorematic parts of statements of the lawlike regularities in which (as we say) the dispositions are manifest.
Trying to unpack this, Lewis is stemming away from Behaviorism to understand the hidden truth about dispositions where there a purely fictitious. I am getting myself caught up in what I believe to be circular reasoning that these dispositions are false but we are still able to conceptualize their construction or manifestation based upon syncategorematic parts. Lewis continues by saying that the causal connection between an experience and its typical occasions have some component of analytic necessity. How does this relate to dispositions?