Che cosa significa "He did not see physics and the metaphysical at opposite sides of the spectrum"

I especially don't understand the "opposite sides of the spectrum" mean ?

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A spectrum is like the spectrum of light, where at one side you have ultraviolet light, and on the other side you have infrared light, and all of the visible colors are in the middle. You can also have ideas on a spectrum, like in politics. The American political spectrum goes from the far-right Trump Republicans to the far-left Green Party, with moderate politicians in the middle. So when he says he doesn't see the two ideas at "opposite sides" of the spectrum, he means they are more similar than they seem. Maybe they are both on the same side. The spectrum he is talking about is the physical-metaphysical realm, where solid objects like humans are on one side and non-tangible things like ghosts are on the other side.