Howard Gardner, a developmental psychologist, made an important observation about human intelligence. That observation was that one’s cognitive abilities provide a view of only one type of intelligence, a general intelligence. Gardner posits a theory that is now well accepted, that there are additional types of intelligence, like musical intelligence, kinesthetic intelligence, intrapersonal intelligence, interpersonal intelligence.
Cognitive: Leadership requires that one be able to assess the current state, envision a better future state, and to determine the strategy, tactics, and actions for bringing that future state into being. This work requires that one be intelligent enough to be able to do each of these things in an environment of accelerating, constant, and disruptive change with limited resources.
Intrapersonal: This is the Ancient Greek admonition: “Know thyself.” The ability to understand one’s own feelings, thoughts, and motivations is a recognized form of intelligence. When a leader knows themselves, they know who they are, their strengths, their deficiencies, and what areas that they may need help. This intelligence is a large part of what allows the leader to develop and utilize the next intelligence.
Interpersonal: The effectiveness of a leader is limited by their ability to lead the people in their charge. This requires a higher than average intelligence when it comes to people. This intelligence is what allows the leader to understand others, to interact with them in ways that cause them to grow, inspiring them to act, and recognizing their feelings. This is the ability to take multiple perspectives, especially 2nd person, 3rd person, and likely even greater numbers.
Moral: Hitler was high enough on the cognitive line. He was also intelligent enough when it came to interpersonal skills. Certainly, we can guess that he was lacking as it pertains to intrapersonal intelligence. But when it comes to moral intelligence, he is one of four or five people in modern times vying for the lowest possible score. Every leader needs a list of non-negotiables, and much of that list will be values. Determining what those values are and building a culture around them requires a moral intelligence.
Of all the human capacities, leadership is surely one of the most demanding. It is also one that requires the development of multiple lines of intelligence that make one an effective leader. You may believe that there are more intelligences necessary to lea, but you are unlikely to be able to subtract from these without also reducing the effectiveness of the leader.