Wherever Aquinas discusses mental life – cognition, perception, thought, knowledge, reasoning – his writing can seem like a trackless wilderness to the uninitiated. The texts overflow with technical Latin terms that come into English as impenetrable jargon: ‘intellect in actuality,’ ‘habit of science,’ ‘sensible species,’ ‘intelligible being,’ ‘intellected intention,’ ‘estimative power,’ ‘word of the heart.’ Even terms corresponding to familiar English terms, such as ‘belief,’ ‘judgment,’ ‘experience,’ ‘passion,’ ‘intention,’ or ‘perception,’ are used in confusing and unexpected ways.