A sacrament for Aquinas, is not merely a preparation for God’s action (dispositional causality) but an instrument, which acts (instrumental causality). This instrument that the sacrament is, has a quality of visibility, not only in the optic sense, but as being presentable and accessible by the senses and the being as a sign. The dimension of signs not only perfuses the line of distinction between the miracle and the sacrament – it creates it. I propose to investigate the role of the signs as intermediaries of instrumental causality and obediential potency (potentia oboedientialis) with a primary focus not on the way change of nature laws, but the laws of signs instead. While, for Aquinas, the logic of non-contradiction holds for every miraculous and sacramental event, so does the reality of signs remain key to the sensible part of experience that allows for the revelation to happen in miraculous and non-miraculous ways depending on how we interpret it. When making this distinction, the focus will not lie, per se, on the nature of things and how it is affected in the sacrament or a miracle. Instead, the focus falls on the interpretive, and, in that sense, semiotic part of the experience, which the sacraments and miracles represent. That interpretative power revolves around the senses (internal and external), a semiotic web to which the experience itself belongs, and a curious phenomenon of semiotic awareness.