  The special composition question (SCQ), which asks under which conditions
objects compose a further object, establishes a central debate in modern
metaphysics. Recent successes of inductive metaphysics, which studies the
implications of the natural sciences for metaphysical problems, suggest that
insights into the SCQ can be gained by investigating the physics of composite
systems. In this work, I show that the minus first law of thermodynamics, which
is concerned with the approach to equilibrium, leads to a new approach to the
SCQ, the thermodynamic composition principle (TCP): Multiple systems in
(generalized) thermal contact compose a single system. This principle, which is
justified based on a systematic classification of possible mereological models
for thermodynamic systems, can form the basis of an inductive argument for
universalism. A formal analysis of the TCP is provided on the basis of
mereotopology, which is a combination of mereology and topology. Here, "thermal
contact" can be analyzed using the mereotopological predicate
"self-connectedness". Self-connectedness has to be defined in terms of
mereological sums to ensure that scattered objects cannot be self-connected.
