Step 1: Understanding the Concept:
This question directly asks for the central theme of the poem 'The Empty Heart' by Periasamy Thooran.
Step 2: Detailed Explanation:
The poem is an allegory about a man who receives a magical pitcher but can never fill it because his desires are infinite. He asks for more and more, but his heart remains "empty" because he is never satisfied.
The poem's fundamental message is that human greed is a bottomless pit. It is an insatiable desire that has no limits and can never be fulfilled. It is, therefore, endless. The man's eventual death from exhaustion in his quest for more proves this point tragically.
Step 3: Final Answer:
Greed is endless.