The Argument from consensus or Argument from common consent can be summarized as follows.
"Throughout the world, in all lands, people believe in some God. And not just now, but in the past, a belief in some God was a very common part of daily life. So the person who denies that God exists is opposing the common consent of all of humanity, that God exists. Who are we to oppose such an enormous consensus? Therefore, God exists."
This argument has a number of problems.
- It's not true that everyone in all times has believed that God exists. There have been dissenters, atheists, everywhere.
- There are a number of different versions of God that people believe in: the gods of the ancient Greeks are very different from the Hindu gods, which are very very different indeed from the spirits that some Africans traditionally worship, which are of course very different still from the Judeo-Christian God. At the very best the most one could say is that some higher power of some sort has been commonly, although not universally, thought to exist.
- The argument as stated does not differentiate between the actual existence of some form of God(s) and the desire for God(s). Widespread belief in God could be a reflection of the fact that God exists, or it could reflect the desire of a community (in this case, humanity) for a protective force to answer difficult questions ranging from the reason for thunder (Thor) to what happens after death (Heaven). Children in many countries believe in Santa Claus, not because he exists, but because they wish he did, and they have been encouraged in their belief by their parents. This highlights another problem:
- Reinforced opinions are still opinions. The established churches in countries across the world have encouraged belief in their tenets throughout history. It is natural for people raised in a tradition to believe that tradition, just as children believe in Santa because parents tell them it's true, and parents don't lie to their children.
- The fact that there is widespread consensus about a topic does not mean that the consensus is correct. A commonly cited example is that most people in medieval Europe believed that the Earth was flat, but that didn't change the fact that the Earth is round. This example is itself an example - the fact that the Earth was round was quite well established in medieval Europe, but not widely discussed because it had no significant impact on people. So our widespread belief about these people in no way affects what they actually knew about the shape of the planet.
These problems have led to argument from common consent being considered an interesting historical perspective on, but not a strong rationalization for, the existence of God.