Confused with reinforcement

Tim Carey (970908. 6.15)

Hi All,

As an ex follower of behaviourism (having done post-graduate studies in
Special Education and taught in special schools for some years) and now
trying to learn and understand PCT I'm finding this conversation about
reinforcement (and the attempt to make links between EAB and PCT)

One of the definitions of a positive reinforcer (and they are all pretty
similar) I have from Martin and Pear (1992, Behaviour Modification: What it
is and how to do it) page 28 is: "A positive reinforcer is an event that
when presented immediately following a behavior, causes the behavior to
increase in frequency. The term positive reinforcer is roughly synonymous
with the word reinforcer."

The locus of causation in this definition seems to me to be the antithesis
of the way causation is described in PCT. I don't understand what the
discussion is about, what am I missing?