Is Space Within the Three Realms or Beyond Them?

The reasoning for this question is as follows: first, clarify the concepts and characteristics of void and the Three Realms (desire, form, and formlessness) along with the six sense faculties. Then, determine whether void belongs to the dharmas of the Three Realms, enabling an accurate and truthful conclusion. Void means emptiness or space, primarily constituted by seeds of the space element. The void formed by seeds of the space element is also called space, characterized by its capacity to contain and support, possessing practical function—it can contain and support material form dharmas. Since it is formed by seeds of the space element, one of the Four Great Elements, void is a form dharma; it has characteristics, albeit the characteristic of being empty and devoid of substance. Void is a form dharma, belonging to the form-at-the-boundary-of-form category. It is perceived by the eye consciousness. Form dharmas perceived by the eye consciousness must have characteristics. However, void has the characteristic of being empty and having nothing, whereas material form dharmas have the characteristic of being non-empty and having color. This part is discussed in the Yogācārabhūmi-śāstra. The characteristic of form-at-the-boundary-of-form differs from that of material form dharmas. When one opens their eyes, they immediately know whether what is before them is empty or not. This empty form dharma is seen by the eye consciousness, and non-empty form dharmas are also seen by the eye consciousness. Emptiness has the characteristic of being empty, and non-empty material form dharmas have the characteristic of being non-empty. If emptiness had no characteristic, how could the eye consciousness discern whether it is empty or not? The definition of the Three Realms is that they consist of dharmas; they are not empty. They include form dharmas, mind dharmas, and dharmas that are neither form nor mind. Mind dharmas and form dharmas are two distinct categories; they do not encompass each other. However, form dharmas are form dharmas within the mind, not dharmas outside the mind. Void is also a dharma within the mind, not outside the mind. Void is also a dharma; it is not non-existent. Therefore, void belongs to the dharmas of the Three Realms. There is only one dharma not within the Three Realms: the self-natured true mind. Since void is a form dharma, has function, and can support material form dharmas, void is certainly within the Three Realms, not outside them. There is definitely no void outside the Three Realms. Void is the emptiness of space. "Turtle's fur and rabbit's horns" represent the nothingness and nonexistent emptiness of absolute non-existence; it is not the emptiness of void. Therefore, "turtle's fur and rabbit's horns" does not involve whether it is inside or outside the Three Realms. Void has no boundary; the worlds of the ten directions are all within void. The Three Realms have boundaries. Having existence and having nothingness constitute the boundaries of the Three Realms. The Three Realms are suffering. Reaching the boundary of suffering, where there are no form dharmas and no seven-consciousness mind dharmas, is the state of Nirvana without residue; this is the boundary of the Three Realms. Nirvana and non-Nirvana constitute the boundary line. Although the mind dharmas of the seven consciousnesses are not within void, they are dharmas within the Three Realms. Tathagatagarbha (Buddha-nature) is not a dharma within the Three Realms, nor is it a dharma outside the Three Realms, because there are no dharmas outside the Three Realms. Arhats in Nirvana, having no form dharmas and no seven-consciousnesses mind dharmas, do not dwell within void. Only form dharmas can dwell within void, and they are also not within the Three Realms.