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Two dimensional existence would include width and height, but no girth. An example would be a piece of paper or a computer screen. One dimensional would have length, but no width or height, a straight line.
We are three dimensional yet can interact with one and two dimensional worlds. These dimensions are unaware of us except that we can interact with them. Would it not be arrogant to assume that there are not dimensions beyond the third?
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Just as we can interact with two dimensional worlds but not exist within them, a fourth dimensional existence would be able to interact upon the third dimension but never truly be a part of it. Consider this is where we pass on to when we die.
Are you with me so far?
Since the fourth dimension does not pass through time as we know it, but is a part of all time, it would mean that we would exist in the third and fourth dimension simultaneously. At first this is a hard concept to grasp. That's because we are time linear beings. It's hard for us to understand time in a non-linear fashion. But if a dead person is in the fourth dimension, a part of all time, then that means that person also exists at a point in time when they were alive in the third dimension.
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Of course, if a fourth dimension exists then that opens the door to infinite dimensions beyond the fourth. Each incremental dimension would be harder and harder for us to grasp. Or maybe we just turn into worm food when we die.