While the ideas of Thomas and Calvin overlap a great deal (more than is often admitted), their agreement does not always seem obvious at the surface level. Certain key words differ in ways that create the appearance of a chasm between the scholastic and the reformer where such does not necessarily exist. Paul Helm has a nice essay that looks at one of those areas: common grace and natural law.
To say that a human ability or activity is the effect of common grace or that it is the working of nature, human nature, are thus two ways of saying the same thing, or almost the same thing. What the phrase 'common grace' brings out is that these abilities and activities, as found in fallen and unregenerate human nature, are the result of undeserved, divine goodness. The effects of the Fall on human nature could have been worse than they are, and why they are not worse than they are is due to God's undeserved goodness. 'Nature' looks at the same phenomenon from another angle, focusing on the persisting structures of human nature.