It often bothers me that most recognized world religions have such disappointingly deficient view of Hinduism. The discussion of Hinduism does not go any further than idol worship paganism. Each temple of India has a different deity with varied figures that it is just not easy to convince anyone that Hinduism may be the most monotheistic religion in the world.
There are numerous issues that exasperate this misconception of a polytheistic religion. Each household believes in a favorite deity called the Ishtadevata. Families will first pay their complete respect and obeisance to this deity before proceeding with anything auspicious. Then within the Hindu families there is also a great divide between which deity is more superior than the other based on their family tradition. Some families will not allow a deity to be worshiped in their household because of various reasons including superstition. There have been great reformers in the past like Swami Dayananda Saraswati who completely discouraged the idol worship practice because of common people’s superstitious beliefs, stringent rituals taken out of context, and distorted view of God. He started Arya Samaj to revive the Vedic tradition avoiding idol worship completely. In the Vedas upon which all of Hinduism is based, God is called the supreme Brahman the source and substratum of all creation.
Priests in the temples are often trained in rituals or Pujas, but most are not universal authorities in the concept of Hinduism. They will have great knowledge about the customs, traditions, and would have memorized impressive lengths of prayers. However a lot of them conform to their own beliefs and their familial culture and fall into the same trap of segregated thinking. The only ones in India who could be a good source of explanation of all the different facets of Hinduism are the true Yogis, who have by the practice of different aspects of Yoga including meditation have realized the ONE TRUE GOD- The supreme Brahman. This Brahman is none other than the monotheistic concept of God as defined in Christianity, Islam, Judaism, etc, etc.
Then the question is how does one explain the so-called polytheistic versions of God in Hinduism? Why then are the Yogis completely at peace with this concept if they do know and have realized the supreme Brahman. The answer to that conflict is also within the practice of Yoga. Yoga is the way to achieve oneness with God. It is just not learning postures to improve overall health. In following the different aspects of Yoga, one has to learn the art of Meditation. Meditation in modern life has become synonymous to learning to concentrate and focus. Contrary to common belief it is the art of realizing oneness with God through deep concentration, while focusing on the spot between the eye brows which is called the seat of knowledge, which in scientific language is your frontal lobe, ironically responsible for all executive functions in the body. Unbelievable powers beyond human perception can be attained by concentrating on this source of knowledge and by learning to divert all sensory input away from the mind’s mental chatter, and by channeling the spiritual energy through the spine to the base of the neck (Medulla which controls breathing and heart beat) to the executive center of the brain.
Similar to people trying to come up with different versions of what Yeti the abominable snowman, not knowing the true shape and form, everyone envisions the form according to their own experience. On the path of seeking God, during meditation, not having known what this God looks, feels, sounds, tastes, or smells like, each of the Yogis envisioned God according to their object of meditation. This is called the Saguna Brahman- the God with form. Each Yogi has imagined God to be of a form that suited his inner concept of who God was. So if one Yogi imagined God to have a big head, and a long nose, and someone who removes obstacles, he envisioned Ganesha. On the other hand another Yogi who conceptualized God with various talents or abilities envisioned a human form with multiple hands, and yet another conceptualizing God as a primary source of knowledge who is also kind and caring envisioned God to be a female imparting knowledge in Saraswati. This is a deep state of consciousness similar to sleep state with awareness. But as one keeps on this path of deep meditation one looses all form and realizes a formless Brahman or the Nirguna Brahman. These are successive steps in the path of attaining spiritual realization called the savikalpa and nirvikalpa samadhi.
At least there is consensus about India being historically a land of mystical Yogis. As I just explained that true Yogis go through a process of realizing God via Saguna and Nirguna Brahman. So they are not perturbed mentally with the idea of various forms of God which in the human perceptual world is so offensive. This also in my opinion indicates that there have been at least as many self-realized Yogis as there are forms of deities in this mystical land we call India or Bharat. Each self-realized Yogi has passed on their vision and understanding of God to their disciples or followers. This form of God has been sometimes been taken out of context because of human ignorance however. Unfortunately the greatest ignorance of all seems to be the belief that Hinduism is a polytheistic religion.