I believe in god if you want to define god as "nature." It's called Evolutionary Naturalism.

That is a coherent position, and Spinoza held something close to it, but it is not theism and it does not do the work the word “God” usually does. The interesting question is what you gain by the relabel.

1. It is a definition, not a discovery. Relabeling nature 'God' does not tell us whether anything stands behind nature. The question at issue is not the word but the referent: is the universe the final reality, or does it point beyond itself? Pantheism and biblical theism answer that differently, and the vocabulary hides the disagreement rather than resolving it.

2. The biblical God is not the cosmos. 'Before the mountains were brought forth... from everlasting to everlasting you are God' (Psalm 90:2). Paul says he does not live in temples made by hands and is not served as though he needed anything, since he gives to all things life and breath (Acts 17:24-25). A God who is distinct from, prior to, and independent of the world is a different claim entirely.

3. If nature is God, then God is not good. Nature is indifferent. Predators tear prey apart, parasites blind children, species go extinct by the million, and earthquakes fall on the just and unjust alike. The God of the Bible stands over against evil and judges it (Habakkuk 1:13). A God identified with the whole cannot do that, because the whole includes the cruelty.

4. It makes the problem of evil worse, not better. If everything is divine, then suffering is not an anomaly to be explained; it is a feature of God's own life. That is not a solution to the problem of evil, it is a refusal to feel it. The objection to theism usually gains its force from a moral standard that pantheism has just dissolved.

5. It leaves the 'why' questions untouched. Why is there something rather than nothing? Why do the constants sit in the narrow range that permits chemistry and stars? Why is the universe intelligible to minds at all? Renaming nature 'divine' answers none of these; it only supplies a devotional tone in place of an explanation.

6. The universe appears to have a beginning. Standard cosmology points to a finite past, which makes the older picture of an eternal, self-sufficient cosmos harder to defend than it was a century ago. Something that begins is not ultimate in the way pantheism requires, and 'In the beginning, God created' (Genesis 1:1) describes a different structure than 'the universe is God.'

7. Impersonality does not easily yield persons. Reason, love, and moral obligation are personal realities, and it is not obvious how a purely impersonal ultimate produces them. A personal source explains persons more naturally than an impersonal one does. That is an argument, not a proof, but it is the kind of consideration that decides worldviews.

8. Information looks like the product of a mind. The cell carries coded instructions, and the cosmos carries a startlingly precise set of constants. Stephen Meyer and Robin Collins argue these are better explained by intelligence than by chance. The claim is contested, and you should hear the critics, but it is a serious argument rather than a slogan.

9. Do not confuse the method with the metaphysics. Methodological naturalism is a useful working rule: study nature as though only natural causes were in play. Philosophical naturalism claims that nature is all there is. The first does not entail the second, and treating it as though it does is the real sleight of hand in this discussion.

10. The testable question is whether this God has spoken. A definition cannot be falsified, so it cannot be argued with, which is its main appeal and its main weakness. The biblical claim is different: that the Creator has made himself known, first in what he made (Romans 1:20) and supremely in a Son (Hebrews 1:1-2). That claim can be investigated.

Calling nature 'God' is a way of saying you find the universe impressive, and fair enough. It is not a way of saying the universe knows you exist. Those are different claims, and only one of them is Christianity.

Sources: William Lane Craig, Reasonable Faith; John Lennox; Stephen Meyer, Signature in the Cell; Baruch Spinoza, Ethics.

Related challenges:
• Doesn’t evolution account for the origin and diversity of life on earth, thereby eliminating the need to appeal to God?
• Doesn’t the fossil evidence support the theory of evolution?
• What about vestigial organs like the appendix, or the gill-slits in fetuses? CERTAINLY you can’t mean to suggest that that makes more sense given theism than evolution, can you?!