  We revisit Duff, Okun, and Veneziano's divergent views on the number of
fundamental constants and argue that the issue can be set to rest by having
spacetime as the starting point. This procedure disentangles the resolution in
what depends on the assumed spacetime (whether relativistic or not) from the
theories built over it. By defining that the number of fundamental constants
equals the minimal number of independent standards necessary to express all
observables, as assumed by Duff, Okun, and Veneziano, it is shown that the same
units fixed by the apparatuses used to construct the spacetimes are enough to
express all observables of the physical laws defined over them. As a result,
the number of fundamental constants equals two in Galilei spacetime and one in
relativistic spacetimes.
