237. Where time and space cease there too ceases physical sensing. But this termination of time and space cannot be expressed as a cessation of the physical or material plane of existence in terms of kilometres or material degrees of measurement; on the contrary, no boundary can be reached along this road at any time, for such a boundary does not exist. One would be able to measure forever kilometre after kilometre, planet after planet and star system after star system without coming to any termination. In this respect the physical or material plane of existence has no limit whatsoever. The boundary of the physical plane of existence begins just at the point where the physical body cannot take itself. As an individual is not able to go to another planet physically, he cannot experience that planet as he can experience the planet on which he lives. He can on occasion see that other planet physically as a small star, but the further sensing of that planet must take place in a spiritual way. We have referred to the latter's first primitive stages as the "world of thought". Through the world of thought the individual can form an idea about that planet. Whether these ideas are right or in accordance with actual fact will depend on the maturity of that individual's spiritual bodies. And we have already seen, regarding the commencement of terrestrial mankind's thought life, it has developed to what we call "science" and this science is the beginning of the experience of the cosmic world. In other words, wherever terrestrial man is prevented from being able to sense physically he will continue his sensing in a different condition. This condition is pure thought, or spirit. So the limit to the physical plane of existence is not to be found in distance (that is, at one or another place), but it is to be found in a condition. As this non-physical condition can be only a spiritual one, we see once again that terrestrial man, on account of his mental life, is also a spiritual being as well as a physical one. And the first perfect result of this mental or spiritual life is the overall experience of the limits of time and space.