welcome phoenix further, as you seem to say, one will get stuck attempting to reason the infinite emptiness of a "tree". it can be reasoned: 1. there is no tree because it is composed bark, roots, leaves, etc, 2. there are no bark, roots, leaves, etc, because they are composed of the earth, water, fire elements, etc; 3. there is no earth, water, fire elements because they is composed of various atoms; But then one gets stuck because these causal factors cannot be broken down any further so the Buddha regarded it sufficient the body is broken down into earth, wind (breath), fire (warmth) & water so the mind can see directly this physical body is not permanent, not something 'solid' and not a 'self'