The inadequacy of the action-causes-action model is also apparent in systems that involve gravitation. The effects of gravity can be understood fully only through reference to an attribute of the entities that attract one another—namely, their mass. The equations of celestial mechanics, for example, cannot accurately and generally describe or predict the motions of bodies unless the mass measurements of those bodies are included, explicitly or implicitly. Gravity is the concept by which we identify a characteristic of material objects. The action that we describe as "falling" is caused by the specific objects involved, such as the earth and an apple.

The action-causes-action model underlies the error known as "determinism." Essentially, the determinist sees all action, including human action, as the product of previous action. Thoughts in particular, including even the belief in determinism itself, are viewed as mere consequences of one's environment and genes. Yet as has been previously noted (see p. 1.3:61, including the "Details" box), our thought must be free of such manipulative influences in order for us to claim any objective, unbiased knowledge, even of determinism itself. The determinist claim is thus inherently self-defeating and must be rejected. An individual's mental action, and his or her physical actions as a consequence, must be volitional, originating in that individual as an independent agent.