Thomas Reid's philosophy of mind, epistemology, and philosophy of language all rely on his account of signs and signification. On Reid's view, some entities play a role of indicating other entities to our minds. In some cases, our sensitivity to this indication is learned through experience, whereas in others, the sensitivity is built in to our natural constitutions. Unlike representation, which was presumed to depend on resemblances and necessary connections, signification is the sort of relationship that can occur without any intrinsic ties between the sign and the thing signified. Of particular interest is the priority Reid gives to natural signs. Reid deploys his robust account of natural signs in a way that allows him to sidestep some skeptical worries common in the early modern period, as well as in grounding “artificial” human languages like English or Cantonese on a more basic human capacity for communication, that is, itself, the result of our sensitivity to natural signs of other people's minds.