Locke is telling us that what makes an action/forbearance voluntary is that it is consequent to a volition, and that what makes an action/forbearance involuntary is that it is performed without a volition. The operative words here are “consequent to” and “without”. What do they mean? (Henceforth, following Locke’s lead, I will not distinguish between actions and forbearances unless the context calls for it.)