Reason is what elevates man from animals. It gives him a capacity to think that no other species has. Many people talk about the supposed intelligence of other species, but they cannot answer why those species are not living in conditions such as man. Reason unifies man's senses and gives him the way to perceive reality. Thus, objectivism rejects the idea of thinking with the heart rather than the brain.
Emotions have no place in reason.
The heart cannot think logically, but is influenced by passions, emotions, and whims. Those who are led by their feelings rather than by pure reason are doomed to fall by their own blindness. Also, reason knows no bounds. With it man can learn anything and everything. Objectivism rejects those who claim that we cannot know anything at all for certain.