Written in Paris between 1840 and 1842 by an auditor not enrolled in the courses of the Faculty of Sciences of Paris, this treatise was never officially presented. We present it here without its appendices, which have not been found.

Introduction

We are, of course, familiar with the three dimensions that govern the physical order: length; width; depth. The object of this treatise is a theory that some might deem bold or even heretical, adding two additional dimensions. It is as a free thinker that I come to deliver the conclusions of my research, as well as concrete avenues of application to exploit the infinite resources offered by these two additional dimensions: Time, and Reality.
For theoretical purposes, and for any future calculation, we shall name length A; width B; depth C; time X; reality Y.

Time

The fourth dimension, Time, is tangible. Indeed, we move with it continuously. Time flows in only one direction, which seems impossible to control if we stick to modern science.
Yet time, like the three "main" dimensions, follows an axis. Thus, when mediocre essayists claim that equally mediocre fictional characters travel "through time" and find themselves halfway around the world, said essayists commit an elementary error in reasoning.

The problem with Time as a dimension is that, assuming it is possible to move freely within it, leaving for another era could engender fatal paradoxes. An informed time traveler should therefore, in my view, take all necessary precautions.

Many paradoxes can result from an ill-orchestrated time travel. A few paradoxes and their possible consequences are examined in Appendix A.

Reality

If we accept Time as a fourth dimension, and if we assume that it is possible to alter it, this is tantamount to saying that it is possible to create new Realities; that is to say, worlds where, someone having moved from a point A of the fourth dimension to a point B of the latter, one or more semantic shifts would have inevitably led to the advent of a new reality, if only by an event as insignificant as the disappearance of an insect, inadvertently crushed by our hypothetical time traveler.

One could go further and consider the existence of other universes far removed from our own. And these universes would be generated by fiction.

This is the theory of Reality as a dimension.
This theory probably has limits, but experiments are necessary to be able to verify it.

Ethics

In my opinion, it is paramount to respect the visited dimension (Era and/or Reality), and not to alter it more than necessary. Thus, with wars, downfalls, and decadence proceeding from the natural course of history, it seems futile to consider preventing such events.

Furthermore, on a human level, our ancestors did not speak the same language as we do. What will it be like for our descendants? It could prove complicated, if not impossible, to dialogue. Let us not speak of what would happen to the reckless traveler who found themselves in a country other than their own, unable to understand the local language if no instant translation technique exists in a given XY coordinate.

Practical Applications

In the current state of science, it does not seem possible to change eras or realities at will. Appendix B contains the design plans for the machine to which I give—quite immodestly, it is true—my name: the Émarne spatio-dimensional shifter. The materials used being of an extraordinary rarity, and the degree of mastery required to design such a machine so demanding, I have no doubt that no one will succeed in reproducing this device. Notwithstanding, I do not recommend it, insofar as it is a prototype machine that presents many risks on a human level, if only because it is currently impossible to configure the era or arrival location with precision.

Wishing not to cause useless losses, I intend to be my own guinea pig. I shall endeavor to arrive in the future, for I have no doubt that the available technologies and knowledge will allow me to complete this study.