This is a rough outline of my philosophical framework. Which gives me a context for all of my experiences and knowledge.
We cannot know much for certain. The one exception is the existence of your subjective experience of reality in this very moment of time. As Rene Descartes put it "Cognito ergo sum."
From there I believe we make probabilistic assertions about the world based on evidence. For example a major question as a conscious entity is where did you come from?
There are an incredible amount of possibilities an imaginative person could conjure, and doubtless infinitely more of which no person could ever conceive.
However there is one explanation for our existence which we have an incredible amount of evidence for. This is the materialistic explanation for our existence.
Your conscious experience has access to an external environment. We observe this environment. We seem to be inexorably tied to this environment. There is an incredible amount of evidence based on millions of man-hours of investigation, that says my conscious experience is emergent of the material world.
An implication of this is that it is incredibly likely that when we die. There is no afterlife. That this subjective experience will come to an end just as it came to a beginning. There will come a time in which the material structure which gives rise to your experience fails. It will loose available energy the last few connections will fire and you will be unaware. Your brain will decompose and everything that makes you up will be gone.
It is still a potentiality that some greater god or alien species will take pity on you. They may find value in your conscious experience and will record it; bringing you into an afterlife alien or divine. However we have very little valid evidence supporting such a possibility. In a practical sense I would be more surprised to die and wake up in an afterlife than to walk in the gas station next door and win a million dollars my very first time playing the lottery.
Phenomenological reality is simply the subjective experience of reality. There are aspects of this reality which are distinct from materialistic reality. They are emergent from materialistic reality and dependent on it however they on meaningful within the context of human experience. The following exist within phenomenological reality, emotion, love, categories, social constructs, social contracts, morality, and spiritual experiences.
This is how I think about Plato's forms and mathematical truths. Conceptual reality is a higher space of logic and mathematics. It is structure and meaning separate to the world and based on simple relationships. Things like the Mandelbrot set and pi exist here. Properties of a numeric or logical system. Principles of systems, of networks, of hierarchies, queues and many other things exist here as properties of underlying principles. Axioms must be created or invented but once they exist and a system exists around them we have created a space containing an infinite number of properties or provable truths.