3 Reasons:
1. To posit that an omniscient god created the universe requires you believe that, in the state of affairs that caused the universe, there existed the knowledge necessary to describe every single imaginable detail about the universe, the position and momentum of every single particle throughout time and space - This means you believe that the state of affairs that caused the universe was vastly more complex than the initial state of the universe affairs it's self.
To say that the universe is so complex that it must have been caused by an even more complex being is entirely irrational.
2. God is inconsistent with our background knowledge - You look at all of the knowledge that we have about minds and beings and it becomes quite abruptly apparent that this "god" is inconsistent with most, if not all of it. For instance, he is an immaterial mind, we have knowledge of billions of minds and no knowledge of immaterial minds, thus to posit one exists is to do so with out any justification. This is not to say that God cannot possibly exist because we have no evidence of immaterial minds, it is to say that you are unjustified in believing that such a thing exists as an explanation for anything.
Using an argument from best explanation "God" entirely fails the category of consistency with background knowledge.
3. The vast majority of conceptions of God simply cannot be coherently expressed, most definitions of deities are either incoherent, impossible, internally inconsistent or just so poorly conceived of that they are literally nonsense. If you want to say that you are rational in believing in God then before we get down to any matters of argument or evidence, epistemic justification and probabilities a concept must be coherently defined - Excuses such as "God is mysterious" or "It is beyond our comprehension" are just other ways of saying "I'm talking shit".
1. To posit that an omniscient god created the universe requires you believe that, in the state of affairs that caused the universe, there existed the knowledge necessary to describe every single imaginable detail about the universe, the position and momentum of every single particle throughout time and space - This means you believe that the state of affairs that caused the universe was vastly more complex than the initial state of the universe affairs it's self.
To say that the universe is so complex that it must have been caused by an even more complex being is entirely irrational.
2. God is inconsistent with our background knowledge - You look at all of the knowledge that we have about minds and beings and it becomes quite abruptly apparent that this "god" is inconsistent with most, if not all of it. For instance, he is an immaterial mind, we have knowledge of billions of minds and no knowledge of immaterial minds, thus to posit one exists is to do so with out any justification. This is not to say that God cannot possibly exist because we have no evidence of immaterial minds, it is to say that you are unjustified in believing that such a thing exists as an explanation for anything.
Using an argument from best explanation "God" entirely fails the category of consistency with background knowledge.
3. The vast majority of conceptions of God simply cannot be coherently expressed, most definitions of deities are either incoherent, impossible, internally inconsistent or just so poorly conceived of that they are literally nonsense. If you want to say that you are rational in believing in God then before we get down to any matters of argument or evidence, epistemic justification and probabilities a concept must be coherently defined - Excuses such as "God is mysterious" or "It is beyond our comprehension" are just other ways of saying "I'm talking shit".
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