Aristotle treats individual substances as ultimate subjects of
predication, and distinguishes such items from composites of a subject
and attribute.  A stock example of the former would be a log, and an
example of the latter a white log.  Although the log and the white log
are numerically one and the same, they are nonetheless treated as
distinct items in the ontology that temporarily coincide.  The
particular substance is a subject for predications, and as such is a
substance, and is distinct from the composite of that subject taken
together with an accidental attribute.  This paper explores the basis
for this distinction by examining the role that the demonstrative
"this" plays in picking out just the subject of which some attribute
is predicated, as well as some problems involved in the attempt to
isolate the subject from the accidental unity of subject and attribute.