Many social scientists see spiritual intelligence as an innate human potential, which lies dormant among individuals and can be fostered, developed and nurtured in a systematic way like any other intelligence - cognitive intelligence, social intelligence and emotional intelligence. Spiritual intelligence, thus, is a human potential about existential and philosophical aspects of life for attaining the goal of human life itself and its relationship with the world.
Here is the ABC of spiritual intelligence.
A: Acquiring an ability to transcend the physical and material through experience and learning about human life and self
B: Being in the heightened states of consciousness to self-observe and self-correct oneself while living life and doing work
C: Capacity of mind developed to the level of wisdom to discern between good and evil so as to sanctify everyday experiences of life.
D: Devise and implement actions by making use of developed spiritual intelligence to solve problems of life
E: Evolving oneself to understand inner life of mind, the higher self as owner of body-mind-senses combine and its relationship with one's existence in the world as universal awareness
Howard Gardner, the profounder of multiple intelligence theory and some other social scientists prefer to call this human potential of achieving the heightened states of consciousness 'Existential Intelligence' as a part of metaphysics since the term 'spiritual' has problematic connotations of religiosity of the eastern cultures. After all, SI is a matter of learning - it's learning and practicing how to activate human potential using contemporary secular principles instead of rotting it in religiosity.