Edmund Husserl, the founder of phenomenology, was Heidegger's teacher in Freiburg. His theory was a new version of Cartesianism with the focus on consciousness as 'subjectivity'. Phenomenology is the examination of consciousness in the flow of experience. It is the study of the intentional structure of experiences, which means that consciousness is oriented towards something else.
Husserl's philosophical method is to subtract external knowledge from the external world (putting it into 'parentheses') which is when the philosopher reflects on how a phenomenon appears to consciousness. When looking at a tree, what remains after making the parentheses is a pure tension between the subject and the object. It is an introspective analysis of experience that attempts to go beyond linguistic expressions or a common understanding of the phenomenon.
Husserl was primarily a mathematician who was interested in the nature of truth more than life's problems. His philosophy seeks certainty, just like Descartes, Hume and Kant. He was looking for an 'Archimedean' point from which to establish a foundation for all knowledge. His interest is focused on the form and need for mathematical and philosophical truths.
His method aims to develop a worldview without prejudice that allows a rational exploration of the interconnections between phenomena. Following the Kantian concept of 'transcendental Ego' Husserl develops a 'transcendental phenomenology' as the foundation of all knowledge.
This is a contribution to epistemology, but it is based on questionable assumptions derived from German idealism.Bertrand Russell explains his epistemological vision in The Problems of Philosophy. He affirms that philosophy is seeking certainty and we assume the certainty of many things that, when we look at them more closely, we realise that they are full of contractions. The more we learn from the world the more we realize that we know little for sure. The question of what our senses tell us lies in the problem of change.
To explain this problem Russell distinguishes between appearance and reality and calls it 'skepticism of the senses'. He gives the example of a table that is perceived based on the light in the room, the distance from the sensor, and how the light reflects from the table to the eyes. The same happens with the texture of the furniture and its shape.
"There is no logical impediment to suppose that life is a dream ..." Bertrand Russell
"A doubt that doubts everything would not be a doubt." Wittgenstein
"The human being is not the lord of beings, but the shepherd of Being." Heidegger