The term 'indifferent to pleasure or pain' can be summarized by the word 'STOIC'. The STOIC philosophy was developed by the ancient Greeks and Romans, and it is based on the idea that one should be indifferent to pleasure and pain. This means that one should not be swayed by either emotion, but instead remain focused on their goals and values. The Stoics believed that this would lead to a life of inner peace and contentment.