Thomas Aquinas holds that the rational soul is not only, like other created immaterial substances, mereologically simple, in that it is completely lacking in any kind of material parts, but also mereologically complex, in that it includes within its composition its own essence, an act of existence, and various powers. Aquinas's account of the mereological complexity of the rational soul introduces several tensions with his understanding of the soul as the substantial form of the body and his larger ontology of the human person. After providing an overview of several key mereological notions operative in Aquinas's thought, and an overview of the mereological simplicity and mereological complexity of immaterial substances in his ontology, I introduce three potential concerns for the Thomistic account, all of which might have been avoided had Aquinas instead understood the rational soul to be entirely mereologically simple—serving as the source and subject of, but bearing some other nonmereological relation to, the aforementioned parts. Though Aquinas does not pursue this simpler solution, I argue that he already has built into his ontology the resources to make such a solution consistent with the rest of his thought.

中文翻译：

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托马斯·阿奎那和理性灵魂的复杂简单

托马斯·阿奎那认为，理性的灵魂不仅像其他被创造的非物质实体一样，在分论上是简单的，因为它完全没有任何物质部分，而且在分论上是复杂的，因为它在其构成中包含了它自己的本质，一个存在的行为，以及各种力量。阿奎那对理性灵魂的分子复杂性的描述与他将灵魂理解为身体的实体形式和他对人类更大的本体论的理解引入了几个张力。在概述了在阿奎那的思想中起作用的几个关键分子概念，以及在他的本体论中对非物质实体的分子学简单性和分子学复杂性的概述之后，我介绍了托马斯主义帐户的三个潜在关注点，如果阿奎那将理性的灵魂理解为完全在分论上是简单的——作为上述部分的源头和主体，但与上述部分有一些其他的非分论关系，所有这些都可以避免。尽管阿奎那不追求这种更简单的解决方案，但我认为他已经在他的本体中建立了资源，以使这种解决方案与他的其余思想一致。