The Division of External Appearances Necessarily Includes External Dharma-Dhātus

If the external form aspect consisted solely of the five sense objects without the dharma-dust, then the images entering the eye would lack reflections. Upright and inverted [images] are dharma-dust; they constitute form. If the external form aspect lacked dharma-dust, what entered the eye would be merely a field of color, devoid of shape, posture, distinction of quality, or texture. Anyone can observe what the images in another person's eyes look like, and thus understand this.

For example, when looking into a mirror, the form outside the mirror is the external form aspect. The mirror receives the reflection of the external form aspect, and the form that appears on the mirror's surface is called the internal form aspect. Without the external form, there would be no form on the mirror; this is the factual reality.

Generally, the form on the mirror is quite similar to the external form aspect. Whatever exists outside, exists on the mirror; whatever the external form is, that is what the mirror's form is. Since the internal form aspect possesses dharma-dust, how could the external form aspect lack it? The Tathāgatagarbha presents images as they truly are. "As they truly are" means identical to the external [reality]. The form, manifest form, and unmanifest form of the external dharma-dust will all be manifested through the mirror, identical to the external form. Whether through direct observations in meditative concentration or logical reasoning, the conclusion remains the same.