Kuntres Mattan Torah, On the Completion of The Zohar

Similarity of form and dissimilarity of form2. The reason is that among material objects that take up space, we interpret cleaving as spatial closeness, and we interpret separation as spatial distance. But among spiritual entities that do not take space, cleaving and separation are not perceived as spatial closeness and spatial distance as they do not take any space at all. Instead, we understand similarity of form between two spiritual entities as cleaving; and we understand separation as a dissimilarity of form between two spiritual entities. Just as the axe cuts a material object into two by severing the pieces from each other, so does dissimilarity of form cut the spiritual entity and divides it into two. If their dissimilarity of form is minor, it is said that they are distant from each other to a small extent. If the change of form is substantial, it is said that they are very far from each other. And if they are opposite in form to each other, it is said that they are diametrically opposite.