Here I want to make it very clear that mathematics is not what many people think it is; it is not a system of mere formulas and theorems; but as beautifully defined by Professor Cassius J. Keyser, in his book _The Human Worth of Rigorous Thinking_ (Columbia University Press, 1916), mathematics is the science of “Exact thought or rigorous thinking,” and one of its distinctive characteristics is “precision, sharpness, completeness of definitions.” This quality alone is sufficient to explain why people generally do not like mathematics and why even some scientists bluntly refuse to have anything to do with problems wherein mathematical reasoning is involved. In the meantime, mathematical philosophy has very little, if anything, to do with mere calculations or with numbers as such or with formulas; it is a philosophy wherein precise, sharp and rigorous thinking is essential. Those who deliberately refuse to think “rigorously”—that is mathematically—in connections where such thinking is possible, commit the sin of preferring the worse to the better; they deliberately violate the supreme law of intellectual rectitude. Here I have to make it clear that for the purpose of Human Engineering the old concepts of matter, space and time are sufficient to start with; they are sufficient in much the same way as they have been sufficient in the old science of mechanics. Figuratively speaking Human Engineering is a higher order of bridge engineering—it aims at the spanning of a gap in practical life as well as in knowledge. The old meanings of matter, space and time were good enough to prevent the collapse of a bridge; the same understanding of space and time as used in this book will protect society and humanity from periodical collapses. The old mechanics lead directly to such a knowledge of the intrinsic laws governing the universe as to suggest the new mechanics. Human Engineering will throw a new light on many old conceptions and will help the study and understanding of matter, space and time in their relative meanings, and perhaps will ultimately lead to an understanding of their absolute meanings.