Phenomenology
Phenomenology is an interpretative methodology that studies the structures of consciousness as experienced from the first-person point of view. The experience, along with enabling conditions, is directed toward an object by virtue of its content or meaning (which represents the object). Phenomenology is not a theory, not a system of thought nor a philosophical position. It is a method.

Continental philosophers (Germany, France) have carried on the interpretive aspects of philosophy whereas the dominate English-speaking philosophers (Britain, North America) have typically shunned interpretative aspect and focused mostly on pragmatic and empiric analytic studies. Another type of interpretative methodology is Hermeneutics which chiefly focuses on the interpretation of biblical texts, wisdom literature, and philosophical texts.

The visual diagram below illustrates the trajectories of philosophical traditions from the 17th-century to the 19th-century (with importance of Immanuel Kant).

The Empirical tradition of English-speaking philosophers (Bacon, Locke, Berkeley, Hume) grew into what is called phenomenology – largely represented in the writings of Auguste Comte, John Stuart Mill and Ernest Mach. Phenomenology is a reaction against mechanistic science which tells us about appearances but not reality. It is a radical form of empiricism in that physical objects cannot justifiably be said to exist in themselves – that physical objects are mind-dependent. Phenomenology as an ontological view of the nature of existence can be traced back to Berkeley and his subjective idealism.

Phenomenology's general theme: scientific criteria or the scientific method should be used in exploring, observing and  judging human knowledge. and human societal structures.  The social scientist is not concerned about molecules, atoms and electrons, but beings living, acting and thinking within a social structure.

Idealism general theme: look at reality through the lens of human self-awareness or of the human spirit with creative freedom. Phenomenology can also exist in 'Idealism' realm – testimony to the claim that phenomenology is ‘more developed, more complex’ (see Transcendental Phenomenology).

Phenomenalism vs. Phenomenology
Phenomenalism is not Phenomenology. An -ism is a position, a feeling, a belief. Phenomenalism is ‘all we know are appearances'. An 'ology is the study of, a science of a subject. A methodological thing.  Phenomenology is the study of phenomena, but not saying that only phenomena can be known.

AQAL Map
Using Integral Theory's AQAL map provides a visual tool to assist in understanding Phenomenalism. Since Phenomenalism claims that that physical objects are reduced to mental objects, it exists in the Individual-Subjective or Upper Left (UL) quadrant.

Over time phenomenology divided into several camps including existential and transcendental phenomenalism.

Transcendental Phenomenology (TPh)
Emmanuel Kant started transcendental philosophy; however it was Edmund Husserl (1859-1938) who refined phenomenology as transcendental-idealist philosophy – similar in many ways to Kant’s Transcendental Idealism (the nuances of the differences is fertile ground for high academic debate and reflection).  Husserlian Transcendental Phenomenology is "the reflective study of the essence of consciousness as experienced from the first-person point of view." TPh takes the intuitive experience of phenomena as its starting point and then to study experience without reference to assumptions posited by experience. Husserl is considered to be the founder of transcendental phenomenology,
An interesting ‘clock & dagger’ story begins after the death of Husserl whose students were alarmed with the Nazis intent to destroy his writings since he was Jewish. Before the Nazis arrived Husserl’s manuscripts (approximately 40,000 pages) and his complete research library were smuggled to the Roman Catholic University of Louvain in Belgium by the Franciscan priest Herman Van Breda. The university became home to the Husserl-Archives of the Higher Institute of Philosophy and a major center for phenomenology studies.

Transcendental phenomenologists: Edmund Husserl (1859-1938), Amadeo Giorgi

Existential Phenomenology
Philosophy must begin from experience but argues for the temporality of personal existence as the framework for analysis of the human condition. Temporality as opposed to a higher non-temporal state of eternity, which is co-extensive with the infinite and eternal now of God (no time on ‘The Other Side’). A "primordial" or "original" time that it is finite. It comes to an end in death. Existential phenomenology differs from transcendental phenomenology by its rejection of the transcendental ego.

Existential phenomenologists:  Martin Heidegger (1889–1976), Hannah Arendt (1906–1975), Emmanuel Levinas (1906–1995), Gabriel Marcel (1889–1973), Jean-Paul Sartre (1905–1980), Paul Ricoeur (1913–2005) and Maurice Merleau-Ponty (1908–1961).

Extreme Phenomenalism
In the late 19th century, an extreme form of phenomenalism was formulated by Austrian physicist Ernst Mach, later developed and refined by the Logical Positivists. Mach rejected the existence of God and denied that phenomena were data experienced by the mind or consciousness of subjects.  He held the view that sensory phenomena were "pure data" whose existence is anterior to any arbitrary distinction between mental and physical categories of phenomena.

Anti-Phenomenalism
Recent academic research (2017) claims that phenomenalist interpretations of Kant are out of fashion. The most common complaint from anti-phenomenalist critics is that a phenomenalist reading of Kant would collapse Kantian idealism into Berkeleyan idealism.
Math and logic are problematic for they are independent of sensory verification (one answer is to consider them conventions of language). Also, ethical (right & wrong) and aesthetic (beauty) statements are neither true nor false because they could not be verified (conflicts with the Verification Principle, a philosophical doctrine fundamental to the school Logical Positivism).

Ironically, one criticism points out that the verification principle itself is not - by its own criteria - meaningful. It is not an analytic truth (a 'convention of language') and neither is there any possible or actual sense experience that could be said to verify it.

Last Word
The various camps of phenomenology take various positions on whether we live in a spiritual or mental universe. There are possible perceptions of objects which are never perceived - although they are capable of being so.  Can one have ‘ESNP’? – Extra Sensory Non-Perception. How does the phenomenologist answer the koan problem in which a tree falls in the forest where no one is around and one is asked, “does it make a noise?” or “does a rainbow exist if no one is around to see it?”.  The Berkeleyan answer is alluded to in the following poem:

There was a young man who said
“God, I find it extremely odd
that a tree as a tree simply ceases to be
when no one is around in the quad.”

“Young man your astonishment’s odd.
I am always in the quad.
So the tree as a tree never ceases to be
Since observed by yours faithfully – God”