Let's take Hinduism for example. A religion where the practice of multiple gods is widely accepted. Yet the Bhagavad Gita (one of their most sacred texts) we can find a core monotheistic message. For example,
Chapter 7:16-25 states;
O best amongst the Bharatas, four kinds of pious people engage in my devotion—the distressed, the seekers after knowledge, the seekers of worldly possessions, and those who are situated in knowledge.
Amongst these, I consider them to be the highest, who worship me with knowledge and are steadfastly and exclusively devoted to me. I am very dear to them and they are dear to me.
Indeed, all those who are devoted to me are indeed noble. But those in knowledge, who are of a steadfast mind, whose intellect is merged in me, and who have made me alone as their supreme goal, I consider as my very self.
After many births of spiritual practice, one who is endowed with knowledge surrenders unto Me, knowing Me to be all that is. Such a great soul is indeed very rare.
Those whose knowledge has been carried away by material desires surrender to the celestial gods. Following their own nature, they worship the devatās, practicing rituals meant to propitiate these celestial personalities.
Whatever celestial form a devotee seeks to worship with faith, I steady the faith of such a devotee in that form.
Endowed with faith, the devotee worships a particular celestial god and obtains the objects of desire. But in reality, I alone arrange these benefits.
But the fruit gained by these people of little understanding is perishable. Those who worship the celestial gods go to the celestial abodes, while My devotees come to Me.
The less intelligent think that I, the Supreme Lord Shree Krishna, was formless earlier and have now assumed this personality. They do not understand the imperishable exalted nature of my personal form.
I am not manifest to everyone, being veiled by my divine Yogmaya energy. Hence, those without knowledge do not know that I am without birth and changeless.
Monotheism. Clear as day
