Thomas Aquinas, Compendium of Theology

This doctrine gives us an insight into the condition of the bodies of the blessed. The soul is both the form and the motive force of the body. In its function as form, the soul is the principle of the body, not only as regards the body's substantial being, but also as regards its proper accidents, which arise in the subject from the union of form with matter. The more dominant the form is, the less can any outside cause interfere with the impression made by the form on matter. We see this verified in the case of fire, whose form, generally accounted the noblest of all elementary forms, confers on fire the power of not being easily diverted from its natural disposition by the influence emanating from any cause.

Since the blessed soul, owing to its union with the first principle of all things, will be raised to the pinnacle of nobility and power, it will communicate substantial existence in the most perfect degree to the body that has been joined to it by divine action. And thus, holding the body completely under its sway, the soul will render the body subtile and spiritual. The soul will also bestow on the body a most noble quality, namely, the radiant beauty of clarity. Further, because of the influence emanating from the soul, the body's stability will not be subject to alteration by any cause; which means that the body will be impassible. Lastly, since the body will be wholly submissive to the soul, as a tool is to him who plies it, it will be endowed with agility. Hence the properties of the bodies belonging to the blessed will be these four: subtility, clarity, impassibility, and agility.

This is the sense of the Apostle's words in I Corinthians 15:42 ff.: In death the body "is sown in corruption, it shall rise in incorruption;" this refers to impassibility. "It is sown in dishonor, it shall rise in glory;" this refers to clarity. "It is sown in weakness, it shall rise in power," and hence will have agility. "It is sown a natural body, it shall rise a spiritual body;" in other words, it will be endowed with subtility.