Just like assert, build, and find, deduce can
take as arguments relation-node pairs, and it can use SNePSUL variables in
place of nodes
(UM§2.11).
However, the variables are denoted with dollar signs
(UM§2.7):
$x.
E.g., to find out who is a canary, not just by asking
Cassie whom she explicitly believes to be a canary, but by asking her to
infer all the canaries she explicitly or implicitly is aware of,
