 While we customarily think of \(\bF=m\ba\) as an empirical assertion, there is a real risk that it turns out merely to be a definition or largely conventional in character. If we think of a force merely as “that which generates acceleration” then the force \(\bF\) is actually defined by the equation \(\bF=m\ba\). We have a particle undergoing some given acceleration \(\ba\), then \(\bF=m\ba\) just defines what \(\bF\) is. The law is not an empirically testable assertation at all, since a force so defined cannot fail to satisfy \(\bF=m\ba\). The problem gets worse if we define the (inertial) mass \(m\) in the usual manner as the ratio \(|\bF|/|\ba\)|. For now we are using the one equation \(\bF=m\ba\) to define two quantities \(\bF\) and \(m\). A given acceleration \(\ba\) at best specifies the ratio \(\bF/m\) but does not specify unique values for \(\bF\) and \(m\) individually.