The correct answer is: A. math is an illusion and that the only reality that which exists mentally
Idealism is a theory that argues that the only reality that exists is mental or spiritual. This means that everything we perceive with our senses, such as objects, people, and events, are not real in themselves, but are only mental constructs.
George Berkeley was an Irish philosopher who is considered one of the most important proponents of idealism. He argued that the only thing that exists is the mind, and that everything else, including physical objects, are ideas in the mind.
Bishop George Berkeley was an English philosopher who also supported idealism. He argued that the only thing that exists is God, and that everything else, including physical objects, are ideas in the mind of God.
Georg Wilhelm Friedrich Hegel was a German philosopher who also supported idealism. He argued that the only thing that exists is the Absolute, and that everything else, including physical objects, are manifestations of the Absolute.
The other options are incorrect. Option B is incorrect because it is a statement of hedonism, which is the theory that pleasure is the only good and pain is the only evil. Option C is incorrect because it is a statement of empiricism, which is the theory that all knowledge is derived from sensory experience. Option D is incorrect because it is a statement of rationalism, which is the theory that all knowledge is derived from reason.