If you look at the relative stability of each scale degree in Western harmony you’ll see that the 4th and 7th are the most instable. In order of stability to instability it looks like this:
1, 5, 3, 6, 2, 4, 7
So 4 and 7 provide the most tension as 4 wants to resolve to 3 and 7 wants to resolve to 8. It the natural kinetics of Western harmony.
But I can see how this “tension” can be interpreted as evil in a Premodern culture. When played as an interval, the tritone splits the octave in two. A perfect metaphor of Buddhism’s Duality and Christianity’s fall from Grace. And that interval is also in the proportion of 5:8, or the golden section, or phi. It naturally occurs in nature but it took a Modern perspective to integrate this interval into art and consciousness.
It’s fascinating to look at from an Integral perspective. An AQAL approach would point out the reduction of the geometry of music to the cultural beliefs of that time.
Premodern: Dissonance = Evil
Modern: Dissonance = Natural
See how we integrated a part of nature that we had excluded? Transcend and Include. The development of cultural harmony is fascinating.