"God is everything" is as valid a definition as any, and it has the advantage that this god demonstrably exists. However, it raises the question of why there should be a separate word for "God". Why not simply say "the universe"?
Pantheists such as these often use the term 'God' as a metaphor for nature, the universe, or for as-of-yet unexplained aspects of physics. Some quotes have been misinterpreted and taken out of context by theists, possibly deliberately, to support an argument from authority.
For example, in support of their beliefs, many Christians quote Einstein when he said, "Subtle is the Lord, but malicious He is not" and "God does not play dice with the universe." There are three problems with this argument:
- In both cases Einstein meant 'Lord' or 'God' as a metaphor for some aspect of nature, not in the sense of a supernatural being.
- In using this argument, theists fail to make the connection between Einstein's beliefs and the god they are trying to represent. Einstein was quite clear that he did not believe in a personal god who interferes with or cares about humanity. Saying that Einstein believed in god, when the theist believes in a god with vastly different qualities and intentions, lends no more support to their point than saying Einstein believed in Zeus.
- Even if Einstein did believe in a personal God, the same one as the theist quoting him believes in, this would amount only to an argument from authority. What Einstein wrote about any subject, even physics, is not gospel. His views on physics are held by modern scientists only insofar as they are supported by evidence. His beliefs about any god are irrelevant.