There are two extremely central, interlinked ideas at the core of Touhou's worldbuilding. The first one is it's unique triple cosmology, and the second is the power of human beliefs. While the triple cosmology is likely influenced by Japanese and Chinese ideas, how the power of belief links into it might be influenced by Western thought.
The triple cosmology of Touhou and it's potential influences
The overall cosmology of Touhou is trifold: there are the Physical, Mental and Memory layers. Physical layer is the material world. Mental layer is the immaterial world. Mental layer is presented as ”moving with the spirit” and it covers things like magic, psyche and mood. The Memory layer represents Karma in a Buddhist sense. It stores the continuity of entities and influences probabilities.
The idea of existence being divided into three different layers or realms might is likely derived from Shinto and Chinese ideas about the world being split into three realms. In Shinto, the world is split into the heavenly realm of Takamanohara ruled by Amerasu Oomikami, the realm of humans, plants and animals and the underworld of Yomi where the dead go. Takamanohara isn't ”heaven-like” in the Western sense, but it's rather a place formed by the separation of light and heavy elements. Yomi isn't hellish or a place for punishment, but rather a gloomy and shadowy realm where all go.
Rather than being separate or discreet, these realms are liminal or parallel. The worlds of humanity and the kami and other supernatural beings can intermingle with each other. It's thought that the spirit worlds are closer to humanity during the matsuri festivals, and that all kinds of spirits linger in liminal places like crossroads, bridges and gates.
The Chinese have a similar cosmology. They see the world as being split into heaven or Tian, the world of humanity or Ren and the underworld of Di. The Chinese interpretation of Tian has a bit different character, as it's thought that the deities there govern both the laws of the universe and the moral laws of humanity. The Taoist and by influence Confucian cosmologies see Tian and Di as two great poles, with the world of humanity sitting in the middle. The powers of Tian and Di are thought to regulate the flow of nature and influence human events. Both forces were are revered in the religious side of Taoism and Confucianism.
It should also be noted that Siberian and Eurasian shamanic traditions have cosmological ideas that are remarkably similar to Japanese and Chinese ones, reflecting shared ancient cultural influences. The shamanic traditions put particular focus into the idea of spirit travel between these realms. One can of course find other triple cosmologies in the world too. They are in fact remarkably common. A familiar split is of course the Christian ideas of Heaven, Earth and Hell.
There is clear Buddhist influence on the idea of the Memory layer. Buddhism in general has varying interpretations on the nature of reality, some of them becoming extremely elaborate and cosmic in scale. Some schools see these different layers as being liminal. For example, the Tendai doctrine sees reality split into ten different worlds. These worlds however were not seen as being separate, but as fluid and potentialy containing other worlds. For example, a human being could be part of human world, but when in a fit of anger he would be seen as being part of animal or demon realm. One could become a ”hungry ghost” not only after death but also in life, and conversely one could become an enlightened being in life as in death.
The power of belief
The division of the world into three layers and how the physical and mental layers interact are extremely relevant to the existence of Gensokyo. Humans exist in the physical layer, but have a great influence on the mental layer, particularly en masse. This causes the power of belief to be very central in Touhou. When people cease to believe in something or something becomes sufficiently forgotten or has had it's existence renounced it can ”pass into fantasy” and go into Gensokyo.
In Gensokyo, the belief from human inhabitants can once more sustain these things. Things that have passed into fantasy range from simple material objects to spirit entities. The exact workings of this process are unknow, as are the criteria for passing into fantasy. It's known that kami that no longer receive faith become unable to manifest their powers, which is the same as death to them. Whether youkai experience something similar or vanish more completely is not known at the moment.
Gensokyo itself was of course built by the youkai in co-operation with the other sages of Gensokyo to sustain their existence. The Great Hakurei Barrier divides ”common sense” from Gensokyo and thus allows things that go against such things to exist again. While the youkai meant Gensokyo for themselves, things like kami, a Buddhist magician sealed away, Taoist immortals and even all kinds of random items have ended up in Gensokyo.
It's implied that the power of human belief in itself might create things like gods and youkai through ”fear and awe of the unknown”. Youkai are variously stated to be either created by the Lunarians or through a more indirect Moon-connected mechanism of youkai being born out of shadows cast by moonlight to whom humans projected their fears on. In Touhou canon, it's said that human imagination keeps on creating youkai up to this day, but that they can not sustain themselves. This is because humans blame things like remote controls going missing or sudden drowsiness on youkai. However, such ill-defined youkai lack a sense of self-identity and vanish as soon as they are born..!
Such power of belief is related to certain ideas from the Western esoteric tradition, which has in turn influenced popular culture that may have influenced ZUN. We will take next a look at these ideas and other references to the Western esoteric tradition found within Touhou.
