What I know about Sikhism is the way the msytic masters of various religions and the isms, who are enlightened souls, contribute in it for the teachings for the soul-evolution. I feel it is the Art of Ascendancy or evolution of soul, such a significant factor that a Sikh, means a learner, does follow it as an ultimate goal of life. A Sikh just by obeying Gurbani is considered and is entitled to be a Singh or Khalsa. The word Khalsa conveys the purity of the heart like that of a saint, the mystic person and the word Singh conveys the disciplined power of dutifulness, mystic discipline of duty the very essence of bravery like that in a soldier.
For females, the word Kaur is to promote the feminist image of word Singh. The purity, power and duty are attributes of soul, our conscience in general, without which the Metaphysics remains the Philosophy, which one knows and understand, without practicing it in the real life. This idea of linking soul, self and spirit with the Sun is very much clear when Gurbani says:
“The Sun is one but the seasons are many, says Shri Guru Nanak Dev ji that the Creator, Waheguru (The Eternal Worthy of Praise) is one yet has similarly many forms. Here the Sun is metaphorically represents the soul and God (Waheguru) as the Spirit. The concept of the soul is like that of the zero. Whenever we add the zeroes the result is zero, similarly all souls added together result in one soul; the Spirit, like a drop of water when added in any number it remains and results in water. The drop of water from the sea and the sea are one at the quality level that the water is same, as the spirit.