Yes, the ideas of the Upanishadic thinkers were significantly different from those of the fatalists and materialists.

The Upanishadic thinkers (c. sixth century BCE onwards) were curious about the meaning of life and the possibility of life after death. They believed in the existence of the self or soul, described as both smaller than a seed and greater than the worlds. Many teachers influenced by Upanishadic thought, like Mahavira and Buddha, emphasized individual agency, suggesting that people could strive to attain liberation from worldly existence.

In contrast, the fatalists (Ajivikas) believed that everything was predetermined. As Makkhali Gosala taught, pleasure and pain could not be altered, and both the wise and foolish would take their predetermined course. They denied the effectiveness of human effort in changing one's destiny.

The materialists (Lokayatas), represented by Ajita Kesakambalin, rejected the concept of afterlife entirely. They believed humans were made of four elements that returned to nature after death, and denied the existence of the soul or any world beyond. They considered talk of gifts and sacrifices as "empty lies."

Thus, while Upanishadic thinkers believed in the soul and individual effort for liberation, fatalists denied human agency, and materialists denied both soul and afterlife.