Recent criticism of higher-dimensional extensions of Einstein's theory isconsidered. This may have some justification as regards string theory, but ismisguided as applied to five-dimensional theories with a large extra dimension.Such theories smoothly embed general relativity, ensuring recovery of thelatter's observational support. When the embedding of spacetime is carried outin accordance with Campbell's theorem, the resulting 5D theory naturallyexplains the origin of classical matter and vacuum energy. Also, constraints onthe equations of motion near a high-energy surface or membrane in the 5Dmanifold lead to quantization and quantum uncertainty. These are major returnson the modest investment of one extra dimension. Instead of fruitless bickeringabout whether it is possible to "see" the fifth dimension, it is suggested thatit be treated on par with other concepts of physics, such as time. The maincriterion for the acceptance of a fifth dimension (or not) should be itsusefulness.
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