Answer: The correct answer is a. Gestalt.
Explanation: Gestalt psychology emphasizes the conception that living things perceive things not as mere individual components but instead as a whole. There is a saying in Gestalt that goes: "The whole is more than the sum of its parts".
In this particular example, Dr. Spire says "I believe that mental experience is best understood as a whole, rather than in term of its parts", which means that mental experiences and processes should not be conceived as separate entities existing in and of itself, but rather as a set of interconnected structures that work as a whole.
In conclusion, the school of thought being described by Dr. Spires is a. Gestalt.