Hume’s Free Floating Impressions Illuminating Nothing For Nobody

by Gary L. Morella

John Locke saw that reason alone could not be the starting point that Descartes had tried to make it in laying new foundations for philosophy. Descartes’s rationalism appealed to many as an alternative to Aristotle, but it gave rise to a simplification of a different and opposing type known as British empiricism. [See Wallace, The Modeling of Nature.] The main champions of this new view were Locke and David Hume.

Locke basically held that all knowledge must begin with sensation. Sensations, or "ideas" as Locke called them, are units that the mind perceives and aggregates into complexes. This process led to qualities that go together, which cannot subsist by themselves. Locke postulated an underlying substrate or substance in which they must inhere. He proposed that the real essence of substance consists in the configurations and motions of insensible particles that will always escape man’s observational powers. Thus, the mind can’t know substance in itself, but only the idea of substance as captured in Locke’s concept of nominal essence, i.e., with what it discerns as the observed properties and relations of bodies. Locke puts the Aristotelian idea of substance in the background to be replaced by a notion that material bodies are nothing more than a cluster of accidents, not far from Darwinism.

Hume raised Locke’s sensations to a higher status; they become the exclusive source of human knowledge. Sensations for Hume are lively perceptions and ideas are the fainter ones with the senses providing man’s unique power of knowing. The senses are incapable of discerning any necessary connectedness between the events they perceive. Hume, like Locke, was skeptical of the idea of substance, taking it to mean only "a collection of particular qualities." However, Locke was willing to count powers among qualities while Hume dispensed with these also, arguing that we can have no impression of any force or power by which an object would be constrained to produce an effect on another. He extended his skepticism further to reject the traditional notion of causality, replacing it with a much weaker notion, that of causation. In his view, all that our senses can perceive are temporal sequences among events and constant conjunctions between them. Since we are unable to discern "necessary connections" in nature, on observing a repetition of similar instances we are led by habit or custom to expect its usual attendant. [See Wallace, The Modeling of Nature.]

Hume retained the terminology of cause and effect, but the best that "causal" knowledge could achieve for him was discerning present or past associations of classes of events. As Wallace points out, this discernment would be powerless to guarantee any human expectations about the future. Hence, in the study of nature, induction would be an untrustworthy guide, the ground for achieving demonstrative knowledge would be removed, and the Aristotelian idea of science would be unattainable.

In both his Treatise of Human Nature and his Inquiry Concerning Human Understanding Hume argued that, in the study of nature, there is no way one can either discover or demonstrate any necessary connection between cause and effect on the basis of a priori reasoning. He saw that such a connection would have to be founded on observable experience, and thus, by implication, on the basis of a posteriori reasoning. Per Wallace, up to this point he was on solid ground, but from then on his theory of knowledge failed him. Hume could not see how ordinary sensory qualities could ever disclose any power or energy within the natures of things that could effect the appearances they present to us. Man’s natural state of ignorance was such, he thought, that natural powers have to remain "secret powers," and, consequently, that the natures underlying them have to remain secret too.

Hume went beyond Locke by arguing that, even if we were to know basic "atomic" arrangements and interactions in a Newtonian mechanics sense, we still could not have certain knowledge of how they produce sensible effects in the bodies of which we have experience. The basic principle behind this contention is that all human knowledge of matters of fact is given in, and arises from, sense impressions. But rather than focusing on the source of such knowledge in the essences of bodies and their powers per Locke, Hume examined how necessity could be found in sequences of events. To establish a necessary connection between events, he argued, one would have to prove that the sequence in which the events occur could not be otherwise. But such a proof can’t be found in experience because we have no sense impression of any force or power by means of which one event will be constrained to produce another. Even though past experience shows that events of type A are invariably followed by events of type B, there is no way we can logically conclude from this experience that the next A will necessarily be followed by a B. We can always imagine the opposite sequence taking place.

Through this type of argument Hume brought into question the key notion of causal efficacy or causal influence, the necessary connection between cause and effect implied in the traditional concept of causality. But he still wished to retain causal terminology, and so he proposed to reformulate the causal relation in different terms – giving rise to his new concept of "causation."

In causation two components, temporal priority of cause over effect and constant conjunction between the two, replace the classical idea of causal efficacy. And, where previously there was thought to be an ontological link between cause and effect, Hume now proposed to replace this by a psychological link. For him, a causal sequence is one in which, upon appearance of an event of type A, we are led to anticipate an event of type B. Solely on the basis of such anticipation are we able to label A-events "causes" and B-events "effects." So, subjectively, the causal relation resides in our anticipation of what is going to occur when we see an event of the first type; objectively, nothing more than temporal priority and constant conjunction are required to characterize the relationship between the two types of events.

The observation is made by Wallace that, in Locke’s and Hume’s theory of knowledge, the knower is proposed as knowing sense impressions or ideas, not as knowing things. Epistemologically this reduces quickly to solipsism, for one can well have an impression and yet have no notion whatever of the reality to which the impression might correspond. For Hume, it seems that knowing becomes like imagining, and real concepts become like logical concepts. But we can always imagine sequences of events that are different from those in reality, and unfortunately what is regarded as logical necessity frequently is not related to necessities found in the real world.

In summary, Hume starts with the two great axioms of modern philosophy: 1) only perceptions are present to the mind leading to a radical idealism where we don’t know things, we’re not in communion with the world but rather only with what’s in our own heads, and 2) whatever is distinct is separable. At the end of Hume’s analysis of experience we’re left with nothing but "free floating impressions." We don’t know if there’s a self, so we can’t have an impression of self. Rather we just have "impressions" per se, and we’re not sure if there is anything attached to them, a rather strange view of the cosmos to say the least.

We might ask "From what impression is an idea derived?" which is problematic from the outset per John Hittinger. Critics of Hume point to the fact that to presume that the meaning of a term must be reduced to sensation is a far cry from an adequate account of human experience and meaning. Phenomenologists would ask "How can we have sensations available to us without a public world of things and people?"

The breakpoint leading to Kant is that the truth of propositions depends upon the source of the proposition. Is it a priori, independent of experience, or a posteriori, depending on experience? We either have relations of ideas a priori reducing to mere logical truth, i.e., tautologies A = A (necessary truth but not telling us anything), or a posteriori, truth depending on experience or matters of fact based on associations of perceptions and experience. The truth is not necessary because the contrary is always possible (conceivable or imaginable). This is what intelligence reduces to for Hume, an association of ideas with Pavlov’s dogs being a prime example, i.e., ring the bell, food will be dispensed. Hume says that humans know that there is no necessary connection between ringing the bell and the bringing of food. All of our knowledge of nature becomes that arbitrary. There is no reason why a law holds; we only know that it is, and can imagine a contrary – so much for the Natural Law of God written on the hearts of man. Hume extends the notion of possibility to such a radical extreme that anything that we can conceive the possibility of shows there’s no necessity at all.

There are some problems. Human understanding is full of non-perceptual factors. If seeing is believing literally, there are many things that we have no strict certitude for. Let’s look at three non-perceptual factors.

1) Being of things, i.e., their substance, as for Hume there exists no grounds whatsoever, rationally or empirically for substance. I close my eyes, and you may be gone. I have no sensation or impression of substance so it’s not a legitimate term scientifically.

2) The power of a cause, or agency as Hume can’t see power. He can’t see the power of heat or flame. He has no real explanation of causal power and why, for example, a paper burns.

3) Uniformity of nature, cause and generality as why should the future resemble the past? There is a problem with induction.

What is Hume’s solution? Custom fills in the blanks and impels us to believe in beings, causes, and nature. Without the influence of custom we should be entirely ignorant of matters of fact beyond what is immediately present to the memory and senses. Custom is a psychological mechanism which spreads vivacity and immediacy from present perception to absent; it fills it all in.

The practical resolution for Hume, per Hittinger, is that one can’t be a pure skeptic but rather must be content to be a moderate skeptic living the mixed life with philosophy correcting common sense and vice-versa. In the end, practical life and instinct must rule over reason and theory with philosophy reduced to an amusement. Classical metaphysics was not in his vocabulary as he denied miracles, refuted proofs of God’s existence due to epistemological problems allowing for no claim of any transcendent order.

Hume’s idea of God can best be summed up by his description, per Hittinger, as "the terror for religion and metaphysics." Hume said "When we run over libraries persuaded of these principles, what havoc must we make. Take in our hand any volume of divinity school or metaphysics and say, does it contain abstract reasoning of quantity or number, No. Does it contain experimental reasoning, science concerning matter and fact, No. Commit it to the flames for it has nothing but sophistry and illusion."

Hume developed a theory of morality with reason being the slave of the passions, a reduction to impression and the sensual. Although murder and various moral norms purport to refer to the objective state of affairs, they refer to our own sentiments of disapproval. Thus, Hume’s morality is an appeal to the sentiment of society whereby he assumes that there exists a universal disapproval of certain acts that violate the liberal code of liberty and property, a transition between a moral sense and utilitarianism. One can help but muse if Hume lived in Clintonian America, might he be shocked to see his moral sense marriage to utilitarianism carried to the extreme of partial birth infanticide with no guarantee that he might have ever seen the light of day due to his mother considering him a choice and not a human being? Such is the "sentiment" of society and the state in the absence of the recognition of a universal natural law that allows the killing of 30,000,000 babies and counting. Adam Smith, in working out an approval for general welfare, was a great admirer of Hume.

We will let a mentor of John Hittinger have the final word on David Hume. Hume is "free floating impressions illuminating nothing for nobody."