 Descartes is careful to not identify ideas as pictures or as visual images, but instead says that they are as it were [tanquam] images of things. This is a long-standing theme, for we find it expressed as early as The World (AT XI 3–6; CSM I 81–2) and the Optics (AT VI 112–13; CSM I 165), and as late as the Principles (AT VIIIA 32–3; CSM I 216–17) and Description of the Human Body (AT XI 255–257; CSM I 322–23), where in these contexts ideas are cast as representing their objects without necessarily resembling them. This is important to the theory, since the idea of cold or the idea of sweet, for example, insofar as they are ideas, represent something to the mind, but they are not visual images. The point holds for other ideas, such as the idea of God, which Descartes explicitly lists in the above passage. The idea of God represents something to the mind (it represents an infinite substance), and in line with traditional theological doctrine, supposing that God is non-spatial and non-temporal, the idea cannot be understood as being a visual image of God.