 It is almost Gospel that quantum gravity is what happens when you reach the Planck scale. The standard refrain is that ‘something peculiar’ happens to our concepts of space, time, and causality at such such scales requiring radical revisions that must be described by the quantum theory of gravity (see, e.g., Rovelli, 2007, p. 1287). However, the arguments underlying this orthodoxy have not been rigorously examined. The usual motivation involves a dimensional analysis argument. The scales at which theories make their mark are set by the values of the fundamental constants. In this way the constants demarcate the domains of applicability of theories: c tells us when specially relativistic effects will become apparent, ℏ tells us when quantum effects will become apparent, and G tells us when gravitational effects will become apparent. As Planck was able to demonstrate in 1899, these constants can be combined so as to uniquely determine a natural, absolute family of units that are independent of all human and terrestrial baggage. The Planck length can be written as (Gℏ/c3)½ and has the value 10−33 in centimeters. Planck was not aware of the relevance of the scale set by the constants to the applicability of general relativity, of course, but Arthur Eddington seems to have been aware (though getting a different value as a result of using Osborn Reynold’s determination for the finest grain believed possible), writing in the March edition of Nature in 1918: