An Austrian philosopher
who at the beginning of the twentieth century created phenomenology
, that is the study of the way things appear
to us, regarded as aspects of the external world that are also constituents of consciousness
Husserl was born on 8 April 1859 in the Jewish village of Prossnitz in Moravia. He studied mathematics and science in Vienna, Berlin, and Lepizig, and in 1886 took psychology at Halle. In that year also he married, and he and his fiancee converted to Christianity. His early works appeared in the Halle years, Philosophy of Arithmetic in 1891 and two volumes of Logische Untersuchungen (Logical Researches) in 1900-1.
He taught at Göttingen from 1901, and Freiburg from 1916 till his retirement in 1928. He died in 1938. The first volume of Ideen (Ideas) appeared in 1913; its full title was "Ideas of a Pure Phenomenology and Phenomenological Philosophy", and he continued to work on the second volume for the rest of his life. It was published only in 1952.
Now for the hard part, describing his philosophy. I know his work only tangentially, and have never read any, and his importance today is probably amplified by Jean-Paul Sartre's adoption of many of Husserl's ideas into his own brand of existentialism, which is where I came across them. Any philosophers reading now are welcome to do this properly after me.
In a division somewhat (and only somewhat) reminiscent of Plato's, Husserl sees different spheres of reality, one of facts and one of essences. The material world is a Sachverhaltnis, an assemblage of states or facts about objects. In a different sphere, there are essential properties or formal relations. Bridging these, and moving around them and between them, is consciousness, the ego (das Ich). I suppose these ideas were also in Karl Popper's mind when he formulated his notions of Worlds 1, 2, and 3, which are similar in division.
But Husserl's phenomenology does not deny or denigrate the interaction. (Other philosophies would say either the material world or the ideal world is the truth.) Rather it is the movement of conscious experience within the other worlds that is important, and if I'm talking utter waffle would the philosophically-inclined please refrain from /msg'ing me, I'm pedalling as fast as I can.
An essence or formal relation may be apprehended all at once. You know what a number is, or an even number, or the colour red. An external, physical object is not to be absorbed like this. It makes itself known gradually, in perspective, with one scene shading into the next. We do not view objects as a set of distinct snapshots, nor yet as a continuous undifferentiated stream of understanding, but rather by what Husserl called Abschattung, "shading off" (or perhaps adumbration). Each perception is linked to the next, and becomes it or succeeds it, and the fuzzy progress of the Abschattungen is our three-dimensional grasp of the thing. (The thing itself is called das Abschattete, "the shaded-off".)
A thing known is a noema (plural noemata). Among the noemata are the objects in the world revealed to us by their Abschattungen, but the knowing mind, the noesis, can also move "upward" along the beam of the ego's spotlight and look at the ideas generated in consciousness by the initial impressions. Ideas, reflections, Abschattungen, noesis itself, can all be noemata, and the ego can move smoothly between observing/knowing them at any level.