The history of human thought may be roughly divided into three periods, each period has gradually evolved from its predecessor. The beginning of one period overlaps the other. As a base for my classification I shall take the relationship between the observer and the observed. . . .
The first period may be called the Greek, or Metaphysical, or PreScientific Period. In this period the observer was everything, the observed did not matter.
The second period may be called the Classical or Semi-Scientific--still reigning in most fields--where the observer was almost nothing and the only thing that mattered was the observed. This tendency gave rise to that which we may call gross empiricism and gross materialism.
The third period may be called the Mathematical, or Scientific Period. . . . In this period mankind will understand (some understand it already) that all that man can know is a joint phenomenon of the observer and the observed. . . .
Someone may ask, How about "intuitions," "emotions," etc.? The answer is simple and positive. It is a fallacy of the old schools to divide man into parcels, elements; all human faculties consist of an inter-connected whole . . . (280) A. K.
The organism is inexplicable without environment. Every characteristic of it has some relation to environmental factors. And particularly the organism as a whole, i. e., the unity and order, the physiological differences, relations and harmonies between its parts, are entirely meaningless except in relation to an external world. (92) CHARLES M. CHILD
In reality it is the brain as a whole which is the centre of association, and the association is the very raison d'être of the nervous system as a whole. (411) HENRI PIPERON
The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are loomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality. (352) H. MINKOWSKI
This assumption is not permissible in atomic physics; the interaction between observer and object causes uncontrollable and large changes in the system being observed, because of the discontinuous changes characteristic of atomic processes. (215) W. HEISENBERG
Well, this is one of the characteristics by which we recognize the facts which yield great results. They are those which allow of these happy innovations of language. The crude fact then is often of no great interest; we may point it out many times without having rendered great services to science. It takes value only when a wiser thinker perceives the relation for which it stands, and symbolizes it by a word. (417) H. POINCARÉ