Bhagavad Gita explicitly details God as the only truth of life. As per Bhagavad Gita other than God Almighty, Brahman nothing existed in cosmos and for this very reason Adi Shankaracharya propounded doctrine of Advaita Vedanta.
As per Bhagavad Gita God Almighty, Brahman is the sum total of all souls atmans in cosmos in their pure form. This collective power of all pure souls’ atmans occupied the size of half a thumb. Brahman, God Almighty is that cosmic energy explosion of which resulted in big bang, creation of present cosmos. From spirituality point of view God Almighty existed in all human beings in miniscule form as their soul atman, the spirit within.
As a human being we could not ever negate existence of God Almighty as most human beings in West did. We exist; we as soul atman exist because God Almighty, Brahman exists. If the big bang had not occurred and all souls’ atmans did not scatter all over cosmos, we would not be present at all. Presence of life in cosmic system indicates existence of God Almighty, Brahman.
The abstract truths of life contained in Bhagavad Gita are understood indulging in contemplation (chintan). Literally one could never understand gist of Bhagavad Gita.
To understand definition of God per se Bhagavad Gita, our 100% faith in God, faith in existence of God is necessary. We also must believe in existence of world of souls’ atmans.
Seeker from six years of age, I not only believed in existence of God but my faith in God Almighty was absolute from the very beginning 100%. For this very reason I could easily indulge in Bhagavad Gita and even Upanishads (independent spiritual treatises) at a younger age.