Noumenal and Phenomenal: What Were Kant’s ‘Two Worlds’?

According to Immanuel Kant, there are two worlds out there: the one that we inhabit, and the one that we can never even fathom. The phenomenal world is the world that we experience. The noumenal world is the world that exists independently from our experience, the world of the ‘things in themselves’.

Immanuel Kant was a German philosopher of the 18th century. His magnum opus, The Critique of Pure Reason, laid the groundwork for German Idealism and influenced many great philosophers and thinkers. Published in 1781, the book explores the limits of our epistemological limitations through a discussion of a priori and a posteriori knowledge. A priori knowledge is knowledge independent from empirical experience while a posteriori knowledge is knowledge based on sense data. The heart of Kant’s discussion of the noumenal and phenomenal worlds lies in his understanding of the interplay of these two forms of knowledge. 

What Structures Our Experience?

Immanuel Kant proposed that our experience of the world is not the product of sense impressions alone, but rather consists of the synthesis of our a priori and a posteriori knowledge. Kant outlines two types of a priori structures that determine our experience of the world: the categories of understanding and the forms of intuition. The categories of understanding are divided into four main categories: relation, quality, quantity, and modality. Each of them includes three subcategories that further elucidate the a priori structures that we impose on sense perception. The forms of our intuition include time and space.

While this may sound strange to our ordinary understanding, it is easy to see why Kant arrived at these conclusions. The information we receive from our senses does not amount to the experience we have of the world. If that were the case, our experience would be that of incomprehensible colors and sounds mixed with unintelligible smells, tastes, and touches. Our sense of the world around us is definitely more than the data we receive from our senses. We live in a world that has structure, continuity, and intelligibility. What Kant is arguing is that these characteristics that comprise our ordinary experience of reality are not properties of what we believe to be ‘the external world’ but are in fact properties of our own cognitive faculties. 

Kant on Noumenon vs. Phenomenon

If our internal cognitive structures determine our experience of everything, to what extent can we claim to know the nature of our world? And what are the implications of Kant’s theory on our faith in science? What do we know about how things actually are? Kant not only argues that we know nothing, but that such knowledge is impossible! He distinguishes between ‘the things in themselves’ and how they appear to us. The ‘thing in itself’ is the thing’s existence independently from our categories of understanding and forms of intuition. According to Kant, ‘things in themselves’ are absolutely unknowable because we cannot transcend our cognitive faculties and their inherent structures. In other words, our knowledge will always be limited because it can never be independent of ourselves as knowers. Kant refers to the ‘things in themselves’ as the noumenon, and refers to the ‘things’ as they appear to us as the phenomenon. 

The Phenomenal World

Although we can’t know the noumenon, we can know what it’s not by understanding the phenomenon. As we’ve seen, the phenomenal world is the synthesis of the information we receive from our five senses and the a priori structures of our cognition that organize that information. Our categories of understanding determine our empirical knowledge. For instance, the relationships we perceive between things around us are not rooted in sense data. There is no evidence that the world operates through cause and effect. Furthermore, our ability to perceive the unity of objects falls under the category of quantity. We can understand the boundaries of an object vis a vis another even though these distinctions are not properties of our sensory information. If we look at a pen, we can experience it as a unified object that is distinct from other objects even though we don’t have visual data of all its dimensions and boundaries.

There is no sensory evidence for the objective existence of time and space. Rather, time and space are subjective structures through which our experience unfolds. That initially sounds like a crazy thought, but it is less odd when we remember the simple nature of our sense data. We do not have a sense that perceives ‘time’ for instance, rather ‘time’ is a sense of continuity that organizes the data we receive from our senses. Although we can never know the noumenal world, it can never hurt to let our imaginations run wild. How would you imagine a world without time, space, forms, and causality?