Do All Religions Follow the Same "God"?
It is a fairly popular idea among a certain strand of tolerant human being that all faiths are fundamentally equal, and that diverse religions share a unified conception of God. These individuals argue that all religions have the same underlying value system and that the superficial trappings can, and should, be looked past in order to see the fundamental oneness at the heart of them all. It is a convenient narrative for side-stepping bigotry and intolerance, and a it is a very nice option for people who want the sentimental support of spiritual belief but the lack the discipline to submit to any established doctrines. That is to say, it is an excellent way to have one's cake and eat it too.
Perhaps the most widely recognized manifestation of this mindset in America is the Unitarian Universalist church, which has no creed beside the vague goal of "spiritual development." Unitarian Universalism is probably the world's best example of a non-religious religion, where no specific creeds or beliefs are required and basically anyone can go to their services for worship, prayer or just to hang out. Seeing the extraordinarily permissive and liberal culture of the Unitarian Universalists, it is difficult to argue that they worship the same God as the more strict Abrahamic faiths, the more cerebral and complex cosmologies of Eastern religions, or the magical mysticism of traditional, tribal spiritual practice.
Even the Abrahamic religions, who all nominally worship the God of Abraham, have dramatically different conceptions of what this God is and how it functions. While they all share a common mythology, each faith has a very different idea of what their God is and what one's responsibilities to it are. While Christians worship a triune God (a rather clever of way both being monotheistic and worshipping a human being), Muslims see God as whole, indivisible and separate from this world. While the God of the Jews has exacting dietary and hygiene standards, the God of the Christians asks only for faith. Even these religions that, according to their own internal logic, follow the same deity are fundamentally contradictory on numerous levels and share an uneasy coexistence where they lie in the same geographical area.
This is to say nothing of hugely complex cosmology of the Hindu tradition, and the numerous subsets of believers and followers that call this faith their own. It is arguably pointless to even call Hinduism a "religion," because it encompasses a vastly complex array of belief and practical systems, does not have a unitary holy text or prophet and is basically a catch-all term for the folk religion of the Indian subcontinent. They share a number of beliefs which primarily involve how one should live a just and noble life. These include karma (the spiritual principle that all events have both causes and consequences), samsara (the cycle of life and rebirth) and to varying extents ahimsa (refraining from violence). For the most part, however, Hindu practitioners have conflicting and often indifferent views about the exact form that Gods take in day to day life, and many subscribe to the overarching principles of the faith while having vastly different views.
It is also worth noting the differences between ancient religions and ones that have survived to modernity - we no longer believe in Zeus or Thor or similar pantheons, but why is that? It is a combination both of the cultures changing and turmoil in Europe after the collapse of the Roman empire and consolidation of the Catholic church, and the fact that most of those pantheons ascribed certain natural phenomena to their deities before we understood said phenomena. When we understood what lightning was, where it came from, and even learned how to harness electricity, it became evident that it's not a deity that creates it, but simply nature. Most religions, most sects within a religion, and especially all of the Abrahamic religions, all make different claims about the characteristics of what "god" is - he could be a transcendental entity that encompasses 3 beings (i.e. the Christian trinity), he could be the leader of the Jewish people and not yet have come down in physical form (Judaism), he could even just be one of many deities (Mormonism). Some believe he predestines people to heaven and hell (Calvinism). Islam and Catholicism further have other traditions and additions to the Bible that even further distance themselves from the validity of the claim of being the "same" religion or even worshiping the "same" deity.
However, a more compelling argument can be made that all religious people (which includes the vast majority of humanity for all of human history) all share the common goal of discovering and appreciating the underlying forces governing the universe. Trapped as we are in our small, vulnerable bodies, our immensely powerful minds find cause to ponder why exactly we exist and what forces are causing our world to function. This practice is possibly one of the few cultural universals of humanity. Human beings are hardwired both for forming communal bonds and interpreting the world according to patterns. Our brains, even in basic everyday matters, subconsciously apply order and form out of even chaotic and random occurrences. Even the most rational people exhibit magical thinking at times, and as outlined in Daniel Kahnenman's seminal book Thinking Fast and Slow, the human mind subconsciously disregards rational information in favor of simplistic solutions that satisfy our inner biases, beliefs or prejudices. Complex questions are discarded by our minds in favor of question that have simplistic answers that we can wrap our minds around. In addition, as communal, linguistic creatures humans have an ingrained capacity to see the world symbolically and to make comparisons and metaphors for understanding the world around them. All people do this, and it is one of the foundation characteristics of any definition of human culture. Religious belief is but a single facet of this, and the unity of world religions is better understood by their common basis in culture rather than their recognition of a common "God."
Even amid the global spread of the monotheistic, Abrahamic faiths, people adapted these religions and their view of God to fit their own previous cultural outlook. Africans who follow both Islam and Christianity adapted their new God and his many saints, prophets and angels to their magical world of witchcraft and sorcery, using his symbols and power to deny the effects of enchantments and curses. Though coming from the Christian tradition and remaining under the firm domination of the Catholic church for centuries, Latin American culture has evolved into a fundamentally magical worldview where images of saints function much the same as the totems that were worshipped by earlier generations of Indigenous Americans. Even certain Buddhists believe that Jesus travelled East to India and spread his teachings there, which of course conforms his teachings to the cultural norms prevalent in India.
All this parallelomania starts to make a lot more sense when we understand religion and faith as the imprinting of cultural metaphors on the world around us as a method for simplifying and understanding said world. The immense mystery that human beings have lived in for millennia, the long years on a seemingly random and indifferent planet, encourage this kind of thinking. Human beings are fundamentally hardwired to recognize patterns in nature and to make predictions about them. In addition, human survival and prosperity rests largely on their ability to cooperate in complex ways toward common goals, and community ritual is an excellent way to do that. Both of these have extremely useful evolutionary functions and tangible benefits to survival in the world. Shamanism, the oldest of all human religious practices has been shown through the work of Michael Winkelman (among others) to have numerous physical and psychological benefits for survival through peer bonding and collective spiritual action. It is also known that both meditation and some types of prayer confer psychological benefits to humans, for example by calming the mind.
The search for God, therefore, might be a manifestation of these several adaptive tendencies in human beings. The form that these beliefs take is merely a representation of the fundamental values of that culture. The daily communal prayers and mandatory donations to the poor of Islam represent the collectivist and egalitarian nature of traditional Arabic society. Buddhism and Taoism (both essentially rejecting the relevance of or veneration for a creator deity) embody principles of harmony and balance characteristic of Indian and Chinese culture respectively. It really makes no sense to essentialize the diverse gamut of human cultural evolution with the cop-out phrase "these belief systems are essentially the same, therefore we can all get along." Each of the major mythological traditions of the world represents a special framework for looking at the world and human beings' place within it. Implying that they are all the same is committing the same fallacy spread by liberal internationalist that all societies are just waiting for "democracy."