It is self-evident that resource allocation is better understood when a distinction is made between what people are willing to do to achieve a purpose and what they will do to achieve the purpose. Yet, motivation theorists have largely ignored this distinction in attempting to understand effort aspects of motivated behavior. An exception is Brehm, who has distinguished potential motivation from motivation intensity. Potential motivation refers to the upper limit of what people would be willing to do to satisfy a motive. It is proposed to vary with factors traditionally thought to determine motive strength (importance). Motivation intensity refers to effort and is proposed to vary proximally with the difficulty of instrumental behavior, first rising and then falling precipitously. In this article, I discuss Brehm's distinction and elaborate on its significance.