道德內在論主張道德判斷與行為動機間有必然的連結。這個立場之所以吸引眾多的擁護者，不是因為它可以被用來反駁道德實在論，而是因為它的最佳版本可以引入「理性」概念，讓道德要求、行動理由與人的理性能力產生緊密連結，擘畫出道德理性論、理由內在論與道德內在論三足鼎立的巨大理論空間，並讓認識理由、回應理由及尊重人性等重要價值保留在其理論建構中。了解道德內在論具有如此巨大的理論空間，有助於廓清道德內在論與外在論間的辯論，並避免不必要的誤導。

Moral internalism is the doctrine that there is a necessary connection between an agent’s moral judgment and his motivation to act in accordance with it. This doctrine is appealing to many philosophers, not because it plays a role in the denial of moral realism, but because the best version of it must be formulated in terms of the notion of rationality. This introduction of rationality allows internalist philosophers to investigate the close connections between morality, reasons and the human capacity of reason. As it turns out moral internalism builds a tremendous theoretical space for moral rationalism and reason internalism to go hand in hand with itself, a space in which the human capacity of reason viz. the capacity to recognize and respond to reasons, and the need to respect other people’s autonomy, are highly valuated and instantiated. With this knowledge of the theoretical space of moral internalism, we are able to see the ways to delve into the disputes between moral internalism and externalism, shunning ill advice that could lead us astray.