In pure science (such as mathematics and physics), the first step is to define all terms and concepts precisely. Neuroscience needs this rigour. For example, when you talk about a hormone or any molecule involved in a particular process, you can measure its various parameters and actions.

But what is an emotion? There are different theories, but no materialistic definition (in the sense that it can be proven beyond doubt).

The meaning of what is an emotion varies according to the culture of the psychologist or philosopher. According to the Romans, emotions have a negative sense of excitement. Quite different from what Stoicism advocates. Since then we have positive and negative emotions. But the only materialistic evidence is the micro-expression associated with these emotions. And the culture you live in is bending your rationality to fit the illusion you believe in.

Fear is even worse. And to call fear an emotion is as irrational as fear itself. Why would evolution favour such a negative behaviour? Because in the face of danger, fear is the worst feeling you can experience. In such a situation, you need to activate all your senses and your computing power; not some irrational panic that clouds your mind and makes you a loser.

You may have guessed that I'm an eliminative materialist :)