Another term for the fourth dimension, time, the sephirah Yesod.

"A point is a cross section of a line. A line is a cross section of a plane. A plane is a cross section of a body. A body is the cross section of a tetra-dimensional body, that is to say, of four dimensions. Every body is tetra-dimensional, has four dimensions. The fourth coordinate or fourth vertical is the basic foundation of all mechanics. Intermolecular space corresponds to the Fourth Dimension. In this three-dimensional world of length, width and height we never see a complete body. We only see sides, planes, angles, etc. Therefore, perception is incomplete and subjective. In the Fourth Dimension, perception is objective. There we see bodies from the front, from the back, from above, from below, from within, from without, that is to say, completely. In the Fourth Dimension, all objects appear simultaneously complete. There, perception is objective." - Samael Aun Weor, The Perfect Matrimony

"The fourth dimension is time. Therefore, whosoever wants to know something about the fourth coordinate, let him study Einstein’s Theory of Relativity. I see you seated and writing at that desk. If you observe that desk, you will see that it has three dimensions, which are length, width and height. Yet, a fourth vertical exists and this one is time itself. How much time has passed since the carpenter built that desk? Thus, the fourth dimension is seen by all the world, because there are no people who do not have a determined number of years. There are newborn children, other people of twenty years, and many elders who only await death. Time in itself has two aspects: First, the chronometrical aspect, that is only superficial, and second, the spatial aspect: this is what is fundamental. Reflect on this; I am not discussing beliefs with you, we are discussing matters which are completely scientific. We need to have only a little bit of maturity in order to understand. The conquest of exterior space, cosmic travel, will be impossible as long as we do not achieve the conquest of time, that is to say, the conquest of the fourth coordinate. If a cosmic ship left our world at the speed of light (300,000 kilometers per second) and after some hours of cosmic travelling returned to the Earth at the same velocity, then you can be absolutely sure, that upon its return, the crew members of the ship would not find the world that they left, but instead, they would find a new world, an Earth more advanced by many thousands of years. This was already demonstrated by Einstein with his mathematical calculations. Therefore, the day in which the men of science invent cosmic ships capable of going beyond the velocity of light, they will have then conquered time, in other words, they will have conquered the fourth dimension. That is all. This world of three dimensions is the outcome of the square of the velocity of light, therefore if we pass beyond the velocity of light, we enter then into the fourth dimension." - Samael Aun Weor, Gazing at the Mystery

"Time in itself is the fourth dimension. This is clear… The fourth coordinate is summarized in two totally defined aspects: the temporal and the spatial. It is unquestionable that the chronometrical aspect of the fourth dimension is just the surface… It is indubitable that the spatial aspect of the fourth vertical is the depth… A fourth vertical always exists within the tridimensional world in which we live. This in itself is time." - Samael Aun Weor, Parsifal Unveiled

"Unquestionably, we know that all chemical-physical phenomena are held by the vital body of planet Earth. It is therefore the vital world, the fourth coordinate, the fourth vertical of the physical world. It is the ethereal world, we say, the tetradimensional zone of this planet in which we live, move, and have our being. Far beyond this vital world there are other regions, but let us first examine well the vital world..." —Samael Aun Weor, The Dimensions of the Tree of Life

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