Imagine if you lived your life inside a painting.
Imagine if the painting where you live is 25,000 miles from the bottom to the top and 15,000 miles wide. It's a beautiful painting, full of colors ... and because you have imagination and curiosity, for as long as you live you're entirely free to walk, drive or swim from one end of the canvas to the other, or from the top to the bottom if you choose, as many times as you like.
But because you live inside a painting you live in a 2D world, and cannot ever leave its surface.
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Flying is out: not only is it impossible for you to move even one brush stroke up from the canvas surface, it's also impossible for you to imagine, much less explain, what a 3D world might be like.
Your brain simply isn't wired to think in three dimensions
Scientists living alongside you in the painting are no better off, because their perceptions are also limited by what they can see, test and explain around them ... in two dimensions. They'll argue that three dimensions cannot exist ... because no experiment can be conceived, much less performed, in 2D that will prove three dimensions exist.
Three dimensions can't fit inside a 2D world. Or be described by 2D brainpans.
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If you lived inside a painting would you argue that God, the creator of the painting and the universe, had to live within two dimensions as well ... the two you're familiar with ... restrained by the same physical limits as you, otherwise he couldn't possibly exist?
Or could God simply be too awesome and big ... that's what infinite means ... to fit inside our 3D box?