Toshihiko Izutsu (1914-1993) was a Japanese born polyglot and philosopher, and was the first to fully translate the Koran into his native tongue (after learning Arabic in an incredibly short time). His key work Sufism and Taoism remains little known outside the world of comparative religion, although he appears to be gaining a wider audience than when I first encountered his writings as a late teenager by way of Toward a Philosophy of Zen Buddhism.
As an undergraduate I was humbled by his description of world religions as being threads of a single web, or what I am here calling, fractals of the Cosmic Heart. Along with devouring the complete works of Idries Shah and D.T. Suzuki (a real pincer movement on a young mind unfamiliar with either Sufism or Zen Buddhism!), it was the visceral reading of Toward a Philosophy of Zen Buddhism that acted as catalyst in the breaking through of my spiritual life. And it was too great an encounter to contain at that time; a brief moment of veridical vision sent me on a twenty year exodus until a dream, in which C.G. Jung commanded me to study his work, allowed for integration to begin. And it was an exodus, to be sure, finally finding a place to incubate itself across time and continents only within the last few years. The heart, while being present always, did not become a living reality until psychotherapy began and that, in turn, transmuted into therapeia theon through descent into the darkness of the unconscious psyche, individual and collective.
However, every descent, katabasis, if it is to be survived, has within it a return journey, an anabasis. By entering the darkness we learn to recognise the light, and from there ascend from Hades. Oftentimes, this is called the heroes' journey, although in truth there is little heroic about it except a dim recognition the journey must be suffered and will reveal its purpose in due course. That being said, one ceases at some indeterminate point to be a kidnapped Persephone and, accustomed to the gloom, starts to interact more as an Inanna, a willing participant in the unfolding struggle. At the end of the beginning of metanoia (the 'akea or repentance of Heraclitus as referenced by Iamblichus), suddenly or gradually, one learns to see that in a spiritual sense we are all imitating Arjuna in a cosmic battle, forever repeating the words of Yahweh to Moses, אֶהְיֶה אֲשֶׁר אֶהְיֶה ('I will be what I will be'). As Arjuna learns through Krishna's teaching, it is not for the human being to know what this becoming will be.
For C.G. Jung this struggle marks a start in the individuation process by which, eventually, we each may find union in the Self. In Christian esotericism, we might describe it as living from and within the Heart of Christ, or, in Buddhism as realising our Buddha-Nature. No matter our cultural, religious and temporal/geographical differences the same archetypal patterns, the same 'threads' recur: the above and the below unite in the heart of the seeker, re-enacting in fractal form what the Cosmic Heart IS.
For another take on the same theme I recommend David Odorisio's short article The Alchemical Heart as a place of gathering and guidance for further research. He weaves succinctly the streams of Jung's alchemical investigations, aspects of the Upanishads and Eastern Orthodox hesychast traditions. Izutsu would, I sincerely feel, appreciate Odorisio's contribution.