Let us now compare these circumstances with those which actually exist in nature or in its observation.  First, it is inherently entirely correct that the measurement or the related process of the subjective perception
is a new entity relative to the physical environment and is not reducible to the latter. Indeed, subjective perception leads us into the intellectual inner life of the individual, which is extra-observational by its very nature
(since it must be taken for granted by any conceivable observation or experiment). (Cf. the discussion above.)  Nevertheless, it is a fundamental requirement of the scientific viewpoint -- the so-called principle of the psycho-physical parallelism -- that it must be possible so to describe the extra-physical process of the subjective perception as if it were in reality in the physical world -- i.e., to assign to its parts equivalent physical processes in the objective environment, in ordinary space. (of course, in this correlating procedure there arises the frequent necessity of localizing some of these processes at points which lie within the portion of space occupied by our own bodies. But this does not alter the fact of their belonging to the "world about us," the objective environment referred to above.)

この世には心的なものと物的なもの、という全く異なる二種類のものがあり（二元論）、かつその両者は相互作用せずに並行して進行している、とする考え方

性質二元論（英：Property Dualism）とは、心身問題に関する形而上学的な理論のひとつで、この世界に存在する実体（physical substance）は一種類だが、それは心的な性質（mental property）と物理的な性質（physical property）という二つの性質を持っているという考え。中立一元論と類似の概念である。

中立一元論（英：Neutral monism）とは、心身問題についての考え方のひとつで、心的だとか物理的だとかいうものは、ある一つの実体、または出来事の、二つの性質のことだとする理論である。性質二元論はほぼ同じ立場である。

it must be possible so to describe the extra-physical process of the subjective perception as if it were in reality in the physical world -- i.e., to assign to its parts equivalent physical processes in the objective environment, in ordinary space.

フェヒナーの哲学思想は、精神と物質はひとつであり宇宙は一つの面から見れば意識、一つの面から見れば物質であるというものである。彼は宇宙を意識的存在と見ることを「昼の見方」、無生物として見ることを「夜の見方」と呼び、夜の見方の眠りに落ちた人々を昼の見方に目覚めさせることを目指した。彼の哲学の反響は小さかったが、その哲学に基づいて構想された、身体と精神（物的エネルギーと心的強度）の関係を研究する精神物理学は大きな反響を呼んだ。

It is very unfortunate that Fechner’s view was baptized “psychophysical parallelism;” he himself preferred the term “identity view.”

かくして19世紀の初頭に入り、ドイツの哲学者フェヒナーにより現代の心身平行論が唱え出されたのであります。

Although Niels Bohr apparently never mentioned it in print, he adopted Fechner's psychophysical parallelism as taught by his philosophy mentor, his father's close friend Harald Höffding. In his successful book Psychology, Höffding had discussed the identity theory at length and praised Fechner as the first "to construct the theory of the relation between the mind and body based on the consequences ensuing from the axiom of the conservation of energy" (Höffding 1893, 92). It is no coincidence that as late as 1932 John von Neumann phrased the distinction made in quantum mechanics between the observer and the system under observation in terms taken from the "principle of psychophysical parallelism."

Here this hypothesis interests us as the most natural determination of the relation between physiology and psychology.  These two sciences deal with the same matter seen from two different sides, and there can no more be dispute between them, than between the observer of the convex and the observer of the concave side of a curve (to make use of a simile employed by Fechner).  Every phenomenon of consciousness gives occasion for a twofold inquiry.  Now the psychical, now the physical, side of the phenomenon is most accessible to us ; but this does not affect the principle of the relation of the two sides to one another.

See also Höffding (1891; 1903). On page 30 of this latter work, Höffding dismisses the term "parallelism" as actually being inappropriate and ambiguous and prefers "identity theory" instead.

同一説（どういつせつ、英: Identity theory）は、心身問題に関する立場の一つで、心の状態や思考プロセスとは、脳の状態やプロセスそのもののことだ、という考え方のこと（英語圏では一般に "Mind is Brain" といった形で、be動詞を強調することによって同一説の持つ考えを提示する）。心脳同一説とも呼ばれる。心の哲学という分野において、物理主義（物的一元論）の一種として、二元論一般と対立する文脈で語られる。

Now quantum mechanics describes events which occur in observed portions  of the world, so long as they do not interact with the observing portion, and does  so by means of process 2 (V.1). But as soon such an interaction does occur—  i.e., a measurement is made—the theory requires application of process 1.  This duality is therefore fundamental to the theory.  Danger, however, lies in  the fact that the principle of psycho-physical parallelism is violated so long as it  is not shown that the boundary between the observed system and the observer  can be displaced arbitrarily, in the sense given above.

In comparison of the third and fourth cases, I was  everything up to the retina of the observer, II was his retina, optic nerve and  brain, III was his abstract “ego.”