  The spin properties of merging black holes observed with gravitational waves
can offer novel information about the origin of these systems. The magnitude
and orientations of black hole spins offer a record of binaries' evolutionary
history, encoding information about massive stellar evolution and the
astrophysical environments in which binary black holes are assembled. Recent
analyses of the binary black hole population have yielded conflicting portraits
of the black hole spin distribution. Some work suggests that black hole spins
are small but non-zero and exhibit a wide range of misalignment angles relative
to binaries' orbital angular momenta. Other work concludes that the majority of
black holes are non-spinning while the remainder are rapidly rotating and
primarily aligned with their orbits. We revisit these conflicting conclusions,
employing a variety of complementary methods to measure the distribution of
spin magnitudes and orientations among binary black hole mergers. We find that
the existence of a sub-population of black hole with vanishing spins is not
required by current data. Should such a sub-population exist, we conclude that
it must contain $\lesssim 60\%$ of binaries. Additionally, we find evidence for
significant spin-orbit misalignment among the binary black hole population,
with some systems exhibiting misalignment angles greater than $90^{\circ}$, and
see no evidence for an approximately spin-aligned sub-population.
