In the following, I will argue (following Feynman) that two conditions are needed for antiparticles to exist in Nature: the first is that the energy of a particle is always positive, and the second is that Nature obeys the principles of relativity.

What is the purpose of antimatter?

Antimatter is used in medicine.

These are injected into the bloodstream, where they are naturally broken down, releasing positrons that meet electrons in the body and annihilate. The annihilations produce gamma rays that are used to construct images.

Why do we have antiparticles?

Antiparticles are created everywhere in the universe where high-energy particle collisions take place. ... Antimatter may exist in relatively large amounts in far-away galaxies due to cosmic inflation in the primordial time of the universe.