This question is closely related to this question and this question and this question.
There is a Sutta in the Pali Canon that seems to explicitly reject that any of the aggregates is real or substantially existent, but instead likening them to a lump of foam, a water bubble, a mirage, a plantain trunk, or an illusion:
“Form is like a lump of foam, Feeling like a water bubble; Perception is like a mirage, Volitions like a plantain trunk, And consciousness like an illusion, So explained the Kinsman of the Sun.
“However one may ponder it And carefully investigate it, It appears but hollow and void When one views it carefully.
“With reference to this body The One of Broad Wisdom has taught That with the abandoning of three things One sees this form discarded.
“When vitality, heat, and consciousness Depart from this physical body, Then it lies there cast away: Food for others, without volition.
“Such is this continuum, This illusion, beguiler of fools. It is taught to be a murderer; Here no substance can be found.
“A bhikkhu with energy aroused Should look upon the aggregates thus, Whether by day or at night, Comprehending, ever mindful.
“He should discard all the fetters And make a refuge for himself; Let him fare as with head ablaze, Yearning for the imperishable state.”
Depending upon the answers to the previous questions I'd be very interested in how Theravada interprets this Sutta. Generally, I'm confused how Theravada interprets these Suttas into a coherent and non-contradictory whole:
- SN 22.85 seems to say that regarding a Realized One as real or genuine is incorrect.
- Itivuttaka 44 seems to say that (as per Ruben2020's answer here) the body is real and genuine.
- SN 22.95 seems to reject that and say the body is to be considered like foam as "void, hollow, insubstantial."
Finally, Mahayana monastics train believing that the substantial difference between Theravada views of anatta and Mahayana views of shunyata is that Theravada regards the aggregates and all external phenomena as real and possessing intrinsic nature or essence.
How do Theravada proponents reconcile all of this?