Kant distinguishes the world as phenomenal and noumenal: the real world that can be understood by conceptualising sense data; In Kant’s terms, we are combining intuitions (sense data) and understanding (reasoning) to form experience. The sense data that we see comes to us like a formless dough. The faculties of our mind are the cookie cutter templates that take this dough and form it into concepts and experience.

The noumenal world is what the world is in itself. The reason we know about the noumenal world is by negation: we recognise the boundary of our knowledge.

Kant agrees with both the empiricists and the rationalists. The empiricists are right to insist that there cannot be knowledge without sensory experience ("intuition"), but they are wrong to say that the mind is a blank slate, for the rationalists are right to insist that there are a priori concepts supplied by our minds. However, the rationalists are wrong to say that a priori concepts are sufficient by themselves for knowledge of the world. So, knowledge is possible only because of the combination of the two.

The ancient Pyrrhonist is an extreme skeptic who suspends judgment from all theories because all philosophical beliefs or doctrines cannot be conclusively justified. The attempt to justify judgements leads to an infinite regress.

The Pyrrhonist will not give in to demands of believing in a theory even if they are 'certified' as truth. He will act according to his natural instincts and the practice of ordinary life, he will abstain from attempting to discover a deeper truth behind appearances.

So what is there to gain from suspending judgement? Tranquility. However, his suspension of judgement is not just making a cautious and deliberate decision, it’s from the realisation that looking for deeper truths is fruitless… knowledge is impossible. No matter the theory or conclusion, the skeptic can always ask “well, is that really so?”

In Ancient Greece, Protagoras held the view that “Man is the measure of all things”; he is taking the relativist view that any claim to knowledge or any judgement in the world is relative to our point of view. He is saying that all the moral values we have and truths are ultimately subjective, we depend on ourselves to come up with definitions as there is no such thing as absolute moral ideals or objective knowledge.

For example, Is it acceptable to slaughter cows? The butcher and those that work with leather would say yes, Those that practice Hinduism or advocate animal rights would say no. Who is correct here? The relativist would say they all are, in accordance with their established beliefs. There is no universal law in nature that says we should act a certain way.

Soren Kierkergaard (1813–1855) was a Lutheran Christian that attempted to show the power of faith over the quest for knowledge and certainty. Through the ages, philosophers have attempted to come to a conclusion if knowledge is attainable and in doing so, moving past the stages of doubt and faith as an insufficient conclusion. However, Kierkegaard believes that we are making a mistake by looking for knowledge because knowledge is beyond the scope of human faculty; humans don’t have the tools to know everything. In terms of God, we cannot decide objectively if they exist but we can decide this matter on subjective grounds.

This is where faith comes in. Faith is a deeply personal subjective experience that involves trust, risk and a leap beyond rational certainty. It’s a passionate commitment to a belief in the absence of conclusive evidence. It’s an independent status, it lies beyond the ethical and cannot be explained in universal or rational terms. It’s not a primitive faculty, it constitutes the highest passion.

This commitment to faith enables us to have a more profound encounter with the truth and the truth is God

William of Ockham (1287-1347) was a medieval philosopher, a Franciscian Christian and an advocate of Nominalism. Nominalism is the view that there is no such thing as universals and that they only exist in the mind. When we speak of universals, they are merely names (from latin: nomina meaning names). So what are universals? Universals are general concepts or characteristics shared by multiple instances or particulars. Ockham says there is no such thing as universals, there’s no evidence and the concept of universals is incoherent to begin with.