For years, the criteria for true knowledge has been a topic of debate among many philosophers. After all, the rise of skepticism created a sweeping wave of doubt that caused many to question previously held beliefs and even the validity of religious institutions. In light of this doubt, two primary schools of thought arose to provide vastly opposing answers to skepticism: rationalism and empiricism. David Hume, an empiricist, proposes that all knowledge is derived from experience. He does this by first explaining the experiential basis of knowledge, then describing the various ways in which we form thoughts. Consequently, he uses this empirical view to explain various phenomena such as space and time, as well as the principle of causation. Hume’s argument not only startled the likes of the common people, but also other philosophers. In particular, Immanuel Kant responds to Hume’s philosophy by acknowledging certain aspects of his views such as a posteriori and a priori knowledge. However, Kant presents a stance that does not fit perfectly in the rationalist or empiricist viewpoint. Rather, he proposes a vastly radical view of the human perception and the nature of reality in an attempt to avoid many of the flaws he saw in the rationalist and empiricist schools of thought. As a result, a journey from Hume’s empiricist view of knowledge to Kant’s response, reveals an interesting intersection between two powerfully influential philosophies and the radical implications they have on how we obtain knowledge about the world around us.
As a concept empiricist, Hume believed that we are born as blank slates and that all ideas therefore originate from our experience. This theme provides the foundation for much of his philosophy. However, in the Enquiry of Human Understanding, Hume provides a detailed explanation of the process by which we obtain knowledge from experience. In particular, he argues that we can divide the source of “all the perceptions of the mind into two classes,” impressions and ideas (MP, 529). Specifically, impressions provide the foundation of our knowledge and occur “when we hear, or see, or feel, or love, or hate, or desire, or will” (MP, 529). Therefore, impressions are revealed to us by all of our sensory perception. Ideas, on the other hand arise when “we reflect on any of those sensations or movements” produced by our impressions (MP, 539). These ideas are manifested in our thoughts that we might not have experienced, such as our imagination. However, Hume maintains that even our ideas are derived from our impressions. This is seen in Hume’s example of a golden mountain, where we combine the impressions of “gold” and “mountain” in order to create the idea of one that could not be experienced directly.1 Thus, ideas are created by the operations of the mind, such as memory and reflection. However, impressions, which stem from our experience, provide the basis for all of our thoughts and ideas.
Once Hume establishes experience as the source of knowledge, he addresses a common issue that might arise from this stance. In particular: How do we come to know about things that we have not observed or sensed? In fact, Hume does acknowledge the possibility for an idea to exist that has no basis in an impression. This is seen in his example of shades of color, where he acknowledges the possibility that we may be able to imagine a distinct shade of color without a supporting impression. Although Hume admits that this is potential objection, he disregards it as a minor singularity and rejects it as a counter-example to his overarching theory of impressions and ideas.
Soon after he describes the process by which we obtain thoughts and ideas, Hume elaborates on the types of knowledge. He does this by arguing that all of what we know can be categorized into one of two types: “relations of ideas” and “matters of fact” (MP, 542). The first type, relations of ideas, are ideas that are “intuitively or demonstratively certain” (MP, 542). In particular, relations of ideas are mental acts of comparison between ideas that are necessarily true, like the fact that a triangle has three sides or that “three times five is equal to the half of thirty” (MP, 542). It is the relations of ideas that allow us to have ideas that are based on the “mere operations of thought.”3 Thus, Hume uses the relations of ideas to explain for the ideas that we might have, such as mathematics, that produce relational ideas that do not require direct experience to verify their truth.
The second type, matters of fact, are ideas that stem directly from our experience and are therefore not necessarily true. In other words, they are such that the “contrary of every matter of fact is still possible, because it can never imply a contradiction” (MP, 542). This type of knowledge is seen in Hume’s example where he asserts: “that the sun will not rise tomorrow is no less intelligible a proposition and implies no more contradiction than the affirmation that it will rise” (MP, 542). Unlike relations of ideas, the mere operations of thought are not enough to establish matters of fact, they must be experienced and are therefore liable to be proven wrong.
Similarly, Kant acknowledges similar divisions between the potential types of knowledge that we can obtain. Like Hume’s division between relations of ideas and matters of fact, Kant categorizes knowledge into that which is derived from experience, a posteriori, and that which is necessary, universal, and independent of experience, a priori.4 However, Kant goes a step further and creates another distinction between analytic and synthetic judgements:
In all judgements in which we think the relation of a subject to the predicate, this relation is possible in two ways. Either the predicate B belongs to the subject A as something that is contained in this concept, or B, though connected withed with concept A, lies quite outside it. In the first case I call the judgement analytic; in the second, synthetic (MP, 724).
An apt example of an analytic judgement can be seen in Kant’s example that “all bodies are extended,” since the concept of extended is already linked to the concept body (MP, 724). Conjointly, Kant describes analytic judgements to also be explicative, since the relationship between the predicate and subject does not create anything new.5 Thus, analytic judgments are those that are true by definition and concept. On the other hand, synthetic judgements are quite the opposite. Rather than be true by definition, synthetic judgements “do add the concept of the subject a predicate that had not been thought in that concept at all” (MP, 724). Thus, Kant describes synthetic judgements to be expansive since they bring into light a new, disconnected concept into the nature of the judgement. This is seen in Kant’s example “all bodies are heavy,” where he describes the concept of heaviness not contained in and “quite different” than the concept of a body (MP, 724).
Although Kant draws these two distinctions, one between a posteriori and a priori and another between analytic and synthetic, they ultimately are related. In fact, Kant makes clear of this connection by explaining that analytic judgments are a priori and synthetic judgements are a posteriori.6 Moreover, this distinction is consistent with Hume’s categorical division between relations of ideas and matters of fact. However, Kant goes a step further, arguing for the existence of synthetic a priori knowledge as the basis of much of our true knowledge. This is seen in Kant’s example of “the proposition: Everything that happens has a cause” (MP, 725). Here Kant shows that the concept of a cause is not strictly a relation of ideas (a priori) since it is an expansive statement, yet we cannot derive its truth from experience (a posteriori) and so it is neither a matter of fact. Unlike Hume, Kant believes in the possibility for synthetic a priori knowledge.
Yet another area of distinction between the Kant and Hume lie in their view of space and time. As a concept empiricist, Hume views space and time as abstract ideas that can be derived from our experience (Treatise, 20). Specifically, he views the concept of space and time as abstract ideas that we can obtain through an abstraction of objective resemblance—the spatiality of an object. Consequently, Hume believes we obtain the concept of spatiality by applying our understanding of the contiguity of space and time: a discrete point can result in a succession of points to form a line and therefore a three-dimensional plane.7 In similar fashion, Hume believes time is also a function of a succession of discrete points, going so far as to say that the property of succession is a “property inseparable from time” (Treatise, 23). Thus, Hume’s view of space and time centers around our experience of discrete points and our ability to abstract notions of volume and motion.
In response to Hume, a potential counterargument lies in the mathematical existence of transcendental numbers. This is seen in the case of the root two and pi, complex numbers that are seemingly impossible to derive from experience. Although Hume does not directly answer this criticism, it reveals an issue in his explanation of the relationship between mathematics, space, and time: that they do not seem to be derived from any direct human experience. This issue is also seen in the concept of infinity, for if Hume’s theory begins with discrete, finite points, then it would be difficult, if not impossible, for humans to have an idea of the concept of infinity.
In comparison, Kant presents a slightly different view of space and time: that they are simply forms of our perception. Rather than base the existence of space and time on our experience, Kant first asserts that “geometry is based upon the pure intuition of space [and] arithmetic brings about its concept of numbers by the successive addition of units in time” (MP, 674). Consequently, because Kant believes mathematics constitute synthetic a priori knowledge, or knowledge that are created by our minds, he concludes that space and time are simply forms our perception. Unlike Hume who believed that we can obtain the notion of space and time through experience, Kant argued that we obtain the idea of space and time through the inherent structure of our own minds. This view constitutes what is labeled as transcendental idealism which is the view that space and time do not exist independently of our minds and rather are the lens by which we see the world. Thus, Kant’s view highlights a key presupposition in Hume’s philosophy: the fact that even Hume’s observations regarding space and time would have inescapably occurred within space and time.
This distinction between Hume and Kant’s philosophies is echoed in their respective theories regarding causation. Hume uses the distinctions between relations of ideas (a priori) and matters of fact (a posteriori) to argue about what can be deemed true knowledge. As mentioned before, Hume deems relations of ideas as “demonstratively certain” (MP, 542). On the contrary, Hume questions the validity of matters of fact which “are not ascertained in the same manner; nor is our evidence of their truth, however great, of a like nature with the foregoing [relations of ideas]” (MP, 542). Hume does this by deconstructing the merit of causation, which he assumes to be the underlying force behind many matters of fact. This is seen in his example of a billiard ball:
The mind can never possibly find the effect in the supposed cause, by the most accurate scrutiny and examination. For the effect is totally different from the cause, and consequently can never be discovered in it. Motion in the second billiard-ball is a quite distinct event from motion in the first; nor is there anything in the one to suggest the smallest hint of the other (MP, 544)
Herein, Hume presents his radical view: that cause and effect are two distinct events. As a result, Hume explains that the concept of causation is caused by our key presupposition that what happens in that past will continue to happen in the future.9 Accordingly, Hume denies the rational or empirical validity of this assumption and therefore presents the Humean Problem.
In response to this Humean Problem, Kant presents an answer similar to his view regarding space and time. On one hand, Kant acknowledges that causal connection cannot be in any way proven through rationale means.10 However, Kant does not view causation as simply a mental habit derived from presuppositions around our experiences: “At the same time, I am very far from holding these concepts to be merely derived from experience and the necessity represented in them to be imaginary and a mere illusion long habit” (MP, 687). Rather, Kant asserts that causation is part of our mental condition and a necessity for us to experience the world and make judgements. Similar to how Kant views space and time, he argues that causation is a priori and an integral part of the human cognitive structure.
Although both Hume and Kant’s arguments span a variety of topics and a milieu of seemingly abstract concepts, an analysis of both their views sheds light on several overarching themes and areas of critique. In particular, it is interesting how Hume consistently presents the viewpoint that all knowledge is ultimately derived from experience, yet oftentimes encounters areas where this viewpoint is difficult to defend. As shown in his acknowledgement of the “shades of color” counter-argument,11 there seem to be quite a few instances where an experiential basis for all knowledge is unrealistic. Furthermore, it is interesting to see how Hume uses “singularity” to discredit a this counter-argument rather than through other, more credible means. After all, the mere singularity of an instance does not necessarily discredit its merit and perhaps if there is one instance, there are other areas where knowledge is derived without experience.
On the other hand, Kant’s philosophy is just as, if not more, vast and complex in its structure. In an attempt to present a viewpoint that lies in the middle of the rationalist and empiricist schools of thought, Kant provides an interesting yet convincing philosophy regarding the human mind and the world around us. An analysis of Kant’s arguments surrounding the role of causality, space, and time in the human cognition seem to reveal authentic truths regarding the presuppositions behind both rationalist and empiricist schools of thought. It is the transformation of what philosophers viewed as “ideas or knowledge” into “intuition” that reveals Kantian philosophy to be interesting, if not insightful. Ironically, although his arguments do not fall within Hume’s empiricist stance, Kant’s view of causality as part of our minds provides nothing less than redemption for the empiricist stance that is essentially deconstructed by the Humean problem. Thus, it is Kant’s bipartisan philosophy that not only impacted both the rationalist and empiricist schools of thought, but also provides valuable insights regarding the fundamental nature of the human mind.
Throughout the age of skepticism, there has been much debate regarding the basis for knowledge. On one hand, David Hume proposed that everything we come to know ultimately stems from our experience. He uses this notion to bring into question the causal laws that presuppose many of a posteriori knowledge today. In response, Immanuel Kant provides his own view of knowledge and highlights the a priori nature of causation as well as space and time. Although Kant’s philosophy cannot be categorized in either the rationalist or empiricist stance, it is interesting to see how he attempts to reconcile both views by analyzing the nature of the human mind. Thus, by looking at Hume and Kant’s viewpoints one is able to not only understand two powerfully influential philosophies, but also gain insights regarding the merit of our everyday presuppositions and how our minds perceive the world around us.
Hume, David. A Treatise of Human Nature. Clarendon Press, 2011.
Watkins, Eric, and Roger Ariew. Modern Philosophy – an Anthology of Primary Sources.