"The only sound foundation we can give to the science of human nature must be based on experience and observation" (Hume).
"Impressions are the original elements of knowledge. Ideas are derived from impressions" (Hume).
"Nature cures me of all philosophical delusions" (Hume).
The Philosophy of David Hume
Hume is considered the most important figure in the 18th century of the philosophical current of empiricism. Empiricism arose as a reaction to the rationalism of the 17th century, thus establishing two opposing philosophical currents on the way in which human beings conceive reality.
Rationalism was born with Descartes. According to rationalism, reason is the only source of knowledge. Rationalists believed in the existence of universal and innate ideas that are independent of experience, which allow us to interpret our environment.
Empiricism was born in Britain in the 17th century with John Locke. According to empiricism, only experience is the source and limit of our knowledge. Empiricists denied the existence of innate knowledge. When we are born the mind is a "tabula rasa" in which there is nothing imprinted. Ideas are representations of reality in our mind. In its beginnings, the great project of empiricism was to discover the origin, validity and extension of human knowledge.
In ancient philosophy, the reference was the external world, ontology. In medieval philosophy the reference was God. Modern philosophy was born with the rationalism-empiricism duality, and man and his mind as the center of philosophical reflection, the internal world, epistemology. Epistemology is the branch of philosophy that deals with the nature of knowledge and how we acquire it.
Hume was a radical empiricist, totally opposed to the rationalist conception of human nature. His empiricist predecessors were Locke and Berkeley, from whom he was strongly influenced. His philosophy clearly influenced Kant, who claimed that Hume's work awakened him from his "dogmatic dreams". He also influenced Darwin and his theory of evolution. He also directly influenced the philosophical current of positivism, a philosophical current that holds that the only valid knowledge is experimentally verifiable scientific knowledge.
Hume was a skeptical philosopher who, without prejudice, tried to reach the ultimate consequences of empiricism by applying the methods of experimental research in the study of human nature, its mind and its understanding, trying to discover its power, its capacity and its limits.
Hume's empiricism can be included in the scope of the Enlightenment, a cultural movement born in France and whose conceptual framework was the French Revolution. Its fundamental thesis is that knowledge makes us free, and that this knowledge is constructed scientifically.
Hume is considered today as the perfect exponent of philosophical naturalism. Philosophical naturalism considers nature as the fundamental and unique principle for understanding reality. Hume was a naturalistic empiricist who renounced appeals to the metaphysical or supernatural to explain human nature.
Hume is also considered the forerunner of cognitive science, the scientific study of the mind.
The "science of man"
Hume sought to develop a "science of man" (or science of human understanding), a kind of fundamental or universal science that would ground all other disciplines (including mathematics and natural philosophy), because all of them are in one way or another linked to man. To this end, he sought the principles common to all of them. This universal science would explain the nature of the ideas we employ and the operations we perform with them. Hume hoped that this science would clarify everything and put an end to the confrontation between the various existing philosophical theories.
Hume wanted to reform the philosophy of his time, which he considered to be in a sorry state, embroiled in endless disputes. The problem was that this philosophy was based on hypotheses, on speculations and inventions, instead of experience and observation. Hume wanted to apply the scientific method, without a priori assumptions, without appealing to metaphysics, with clear arguments, easy to understand. In the introduction to his "Treatise" (Treatise of Human Understanding) −considered as his most important work− he proposed "a complete system of the sciences based on an entirely new foundation": the scientific study of human nature.
Although Hume does not expressly mention it, he was strongly influenced by Newton. Hume accepted the maxim "Hypothesis non fingo" (I do not hypothesize), a famous phrase employed by Newton in his essay "The General Scholium", which was published in the second edition of his work "Philosophiae Naturalis Principia Mathematica". A scholium, in Latin) is a note or brief commentary inserted in a document or publication. Newton's note was his response to those who demanded an explanation of the cause of gravity, beyond the mathematical laws governing this phenomenon.
According to Newton, scientific methodology must be primarily experimental and inductive. All laws of nature must be discovered by observation and experiment. For Hume, the only valid method is the one that Newton applied to the physical world, and it is the method that had to be applied to the science of man.
Hume describes his scientific study of human nature as a kind of "mental geography" or "anatomy of mind." But Hume wanted to go beyond a simple description of the mind. He wanted to discover its "secret principles." He wanted to discover in the inner world, the world of the mind, laws like those Newton discovered for the physical world. Newton's achievement was to be able to explain the diversity and complexity of physical phenomena by means of a few general principles, a few laws of economy, a few simple laws.
Hume also wanted to explain all mental phenomena from the smallest possible number of simple and general or universal principles, but all of them derived from experience. He believed that everything, including the mind, was accessible to experience.
Perception
Hume's empiricist ontology is very simple: perception is the only entity that exists. All the contents of the mind come from perception, from sensible experience.
Perceptions are distinct entities, distinguishable from one another. For example, there is a clear difference between perceiving physical pain and perceiving a sunset. And the same is true of ideas, the perceptions of the mind.
Perceptions can be simple or complex. Simple perceptions are those in which no parts can be distinguished. Complex perceptions are those whose components can be distinguished.
There are two types of percepts: impressions and ideas.
Impressions
Impressions are the fundamental perceptions. They are the data of the senses, of the experience of the external physical world.
Impressions can be of two types: sensations and reflections. Sensations (or primary impressions) correspond to the action of the senses, including the sensations of pain and pleasure. Reflections (or secondary impressions) are those produced by the internal exercise of the mind.
Impressions can be simple or complex. A simple impression is, for example, the perception of a color. A complex impression is, for example, the perception of a city or listening to a symphony.
Ideas
Ideas are reproductions or blurred images of impressions. The difference that exists between impressions and ideas is simply the intensity with which we perceive them. Impressions are more intense mental contents. Ideas are less intense mental contents.
Ideas are the memory of the absent object. They are abstract and immaterial realities that guide us in the knowledge and recognition of things. Ideas are nothing concrete. They are at once all the particulars of a group which produce in the mind very similar impressions.
The relation that exists between impressions and ideas is the same as that between original and copy. Impressions are the original elements of knowledge. Ideas are derived from impressions.
Ideas are copies or faded representations of impressions in the mind, and bear some resemblance to impressions. They are mental images generated by impressions. The nature of ideas is more ambiguous and abstract, lacking the details that correspond to particular impressions.
The "principle of copying" is the first principle of the science of human nature. This principle is an empirical thesis that Hume justifies with a counterexample:
Imagine someone who has had experience of all colors except a certain degree of blue. If we present to that person in order all the degrees of blue that exist, from the darkest to the lightest, he will immediately detect that that degree of blue which he has not experienced is missing.
Ideas, like impressions, can be simple or complex. Simple ideas are copies of simple impressions, such as the idea of a color. Complex ideas may be copies of complex impressions, or they may be worked out by the mind from other simple or complex ideas by the operation of mixing or combining them.
Simple ideas are always reflections of the same impressions. Complex ideas do not exactly reflect complex impressions.
Simple ideas derive from simple impressions. Complex ideas derive from complex impressions. There is an exact correspondence between a simple idea and a simple impression. Simple impressions precede and are the cause of the corresponding simple ideas.
Hume's position is contrary to that of Plato, according to whom ideas are the cause of the objects we perceive being a certain way; ideas are the models of objects; objects are imperfect copies of ideas. It is a process of descending causality: from ideas to perceptions.
Hume's thought is more like Aristotle's: ideas are abstractions of sensible objects. It is a process of ascending causality: from perceptions to ideas.
The laws of association of ideas
Ideas (or mental contents) are linked together. An idea attracts other ideas, just as in the physical world a body attracts other bodies by the action of gravity. The forces that bind one idea to another are "soft forces". As a consequence of these forces, ideas follow one another in our mind. Thanks to the natural connections between ideas, we spontaneously form complex ideas from simple ideas.
Following Newton's success with his law of universal gravitation, Hume also elaborated laws of the mind, descriptive laws, not explanatory ones, as is the case with gravitation, which is known to work, but its cause is unknown. From the laws (or general principles) of association of ideas, Hume intended to elaborate a general or universal theory of human nature.
The laws of association of ideas regulate the passage from one idea to another, and are founded on imagination, not on reason. These laws are not deterministic laws, but are governed by probability. Of the association of ideas we know only their effects, not their causes.
Ideas are combined by laws of association. The laws of association of ideas are three: the law of similarity, the law of contiguity in time and space, and the law of cause and effect.
Law of similarity.
Impressions can share common properties. This also produces similarity in the ideas that correspond to those impressions.
Our mind tends to reproduce similar ideas. For example, a portrait leads naturally or spontaneously to think of the original, or a painting leads our mind towards what is represented.
Law of contiguity.
Ideas that have been experienced together tend to appear together. This law underlies the formation of complex ideas. For example, when we perceive an object that has wheels, body, steering wheel, etc. it leads to the complex idea "car".
Law of causality (or cause and effect).
The principle of causality, in its general sense, states that everything that exists must have a cause for its existence. In its particular sense it is associated with natural phenomena.
This law is the only one of the three laws of association that would allow an inference beyond sensory data. But Hume denies it, he did not believe in causation because he claims that it is only association of ideas. There is no impression of the nexus between cause and effect.
Indeed, after the observation of the existence of spatial contiguity of two events, of their succession in time, and of the repeated experience of this relationship between the two, the predisposition is created in our mind to evoke the idea of the second (which we consider "effect") if the idea of the first (which we consider "cause") is present.
Causes and effects cannot be discovered by reason, but by experience. For example, if we hear a voice in the dark, we are sure of the presence of a person.
Causality is not a real thing. It is only an operation of our mind based on habit or habit of observation. It is only an association of ideas by contiguity of phenomena. Therefore, all natural phenomena are based on "beliefs".
Belief is a deep feeling that accompanies a persistent association of ideas. Even believing that things continue to exist when they are not perceived is also a belief.
Actually the three laws of association of ideas reduce to two, for the law of cause and effect reduces to the regular contiguity between two events in space and time.
Knowledge
Knowledge derives only from experience. The limit of our knowledge is impressions and their effects (ideas). The natural sciences are based on statements that only make sense when they refer to a possible experience.
Hume's theory of knowledge is called "phenomenism" because it reduces reality to the only phenomena, which are impressions. We can only be sure of nothing but impressions.
An idea is true if we can point to the impression from which it derives, since our limit of our knowledge is impressions. An idea is false if there is no corresponding impression.
For Hume, induction is always incomplete, in view of the impossibility of proving all particular cases. This position coincides with that of Popper and Kuhn, who consider that there is no justification for going from particular statements to universal statements.
Hume was a nominalist, like Occam: there are no general ideas. There are only particular ideas linked by resemblance and which are associated, for convenience, with a term of language.
Relations of ideas and matters of fact
Following the distinction made by Leibniz between truths of reason and truths of fact, Hume distinguishes two kinds of knowledge: relations of ideas and matters of fact.
In relations of ideas, the principle of contradiction is the guide to determine their truth or falsity. Corresponding propositions can be proved by means of logic.
Relations of ideas express truths of reason, formal relations between ideas without appeal to questions of existence or fact, i.e., independently of what may exist in the physical world. They are necessary relations. They belong to the formal sciences of geometry, arithmetic and algebra. Relations of ideas derive from logic, by reasoning, without recourse to experience. For example, the Pythagorean theorem (geometry), 2+2 = 4 (arithmetic) and a+a = 2a (algebra).
Questions of fact depend only on experiences, and it is not possible to arrive at them by reasoning. They cannot be investigated in the same way as relations of ideas, because the contrary of a fact is, in principle, always possible and does not involve contradiction. There is no contradiction in the proposition "The sun will not rise tomorrow" nor is it less intelligible than "The sun will rise tomorrow." The corresponding propositions are governed only by probabilities. Hume denies that there is absolutely firm knowledge, including scientific knowledge, for all our knowledge is governed by probability; we have no certain knowledge, but only probable knowledge.
All laws of nature could be different from the way they are; it is conceivable. All reasoning concerning matters of fact seems to be based on cause and effect. In matters of fact there is no certain knowledge. Universality and necessity only fit in the formal sciences. Real science is governed by probability.
Memory and imagination
Hume admitted the existence of the faculty of memory, along with imagination.
Memory reproduces impressions, they keep the order and form of the original impressions.
Imagination is the faculty of combining simple ideas to create complex ideas, thus generating the "objects" of our daily experience. Thinking and reasoning are born of imagination.
The interaction between imagination and memory is responsible for fictions, things that do not exist (such as the concepts of substance, personal identity, and causal relationships), which are produced in reaction to the three laws of association of ideas: similarity, contiguity, and causality.
Imagination is subject to the laws of association of ideas. The principles of association of ideas guide the activities of the imagination, impose themselves on the imagination, determine it, order it, make it appear as memory, understanding, fantasy, and so on.
When the mind receives impressions, they can appear in two ways: as memory or as imagination. The ideas of memory are stronger than those of imagination, for memory preserves the order and form of the originals. Imagination, however, is free to alter and disrupt the ideas.
Imagination is creative and unlimited. It can combine incongruous forms and appearances, beyond the universe and conceive of what it has never seen or heard of. The creative power of the imagination is reduced to the faculty of blending, transposing, augmenting or diminishing perceptions. Nothing is beyond the power of imagination except that which implies contradiction.
The external world
Empiricism presupposes, in general, the acceptance of the existence of a world external to the subject, which is the cause of his impressions. Locke had accepted the existence of the world by asserting that extramental reality is the cause of impressions. Berkeley was an advocate of idealism; he did not believe in an external world, only in perceptions.
According to Hume's radical analysis, experience does not imply the existence of an external world, but this interpretation can be accepted as a concession to common sense, because it is a reasonable and deeply held belief, but one that cannot be demonstrated. We know that we have impressions, but we do not know where they come from. We cannot demonstrate that impressions correspond to an extramental reality. Reality is beyond our reach.
Substance
In philosophy, substance is the foundation of reality, of all that exists, that which sustains surface phenomena.
Hume calls into question the idea of substance, an idea that had been the mainstay of Western metaphysics, because there is no impression on which to base it. There is no "substance of mind." If there were such a substance, it would account, among other things, for personal identity. Not only is there no idea of mind as substance, but there is no need for it either, since perceptions exist by themselves.
The substance of mind is only a set of particular ideas or impressions which we receive at any given moment and which we usually find united or which unite the imagination. This is the theory known as the "bundle theory" of personal identity. A person can be considered as nothing more than a bundle of different perceptions that follow one another in perpetual flux and movement. The mind is like a theater where perceptions appear in succession. It is a theater whose location we ignore and of which we do not know what it is made of.
Descartes and Locke had accepted the existence of the reality of the "I", of which we have an intuitive, immediate and evident certainty. Descartes believed in the existence of the soul as the essence of the human being, considering it an immaterial, inextensive and eternal substance.
Hume went further, denying the objective validity of the "I", for there is no impression, which, moreover, should be constant. We cannot be certain that the soul, the self, or the mind exists, because we cannot point to the impressions from which those ideas derive.
Locke said that God was the cause of our existence. Berkeley said that God is the cause of our impressions. For Hume, there are no causes, so there is no God.
Hume did not believe in freedom. For him there is no freedom because to choose among several alternatives would require a mind to choose. But the mind is nothing but a succession of mental states. Freedom and causality are only fictions created by the human mind to order the world, fictions associated with habit and routine.
Physics and metaphysics
We have the idea of material objects because we experience them as perceptions. We also have the idea of space because we experience it: space is constituted by perceptible elements.
Metaphysics has never been a science, but a vain desire to penetrate the impenetrable. It is necessary to liquidate forever the unapproachable metaphysical questions.
This questioning of metaphysics as knowledge would reach its culmination in the 20th century, with the current of logical positivism (or logical empiricism).
MENTAL vs. Hume's Philosophy
Internal world - external world.
According to Hume, there is a close relationship between the external world and the internal world, where the external world is the principal (or primary) world and the internal world, a subordinate world and reflection of the external one. Both are linked by perceptions.
From the MENTAL paradigm, nature is not the fundamental principle, it is not the foundation of all knowledge. Nature is only a manifestation of the archetypes of primaries. MENTAL is the true "substance", the foundation of all that exists, of all sciences and possible worlds.
Laws of the mind.
For Hume, the laws of mind are the laws of association of ideas. But the deepest and most abstract laws are those between the primary archetypes.
The mind is founded on degrees of freedom, which are the primary archetypes. With them, for example, mathematical expressions and computer applications can be constructed.
Hume searched for the laws that govern the mind, but he failed to discover its essence. The essence of the mind is based precisely on the degrees of freedom, which are the primary archetypes.
Imagination.
For Hume, imagination is subject to the laws of mind and there can be no contradiction. In MENTAL, imagination is also subject to the primary archetypes, but "imaginary expressions" can be constructed in the combinatorics of the primary archetypes.
Union of opposites.
MENTAL harmonizes rationalism and empiricism, as well as ontology and epistemology. Inner world and outer world are manifestations of the primary archetypes. Internal world and external world have the same foundation: the primary archetypes.
Theory of mind.
Hume attempted to develop a theory of mind. MENTAL is a theory and model of mind based on primary archetypes. And it is a universal paradigm, as well as the foundation of formal sciences and philosophy as primitives are also philosophical categories.
Simplicity and complexity.
Hume wanted to discover the fundamental simple ideas and how these combine to create complex ideas. He intuited that the foundation of the mind should be simple and that also its combinatorics should be simple.
The foundation of MENTAL is simple: the primary archetypes, which are clear and simple concepts. Their combinatorics are also the primary archetypes themselves, which produce expressions of any degree of complexity. These archetypes are independent of each other, but combine to create universal laws.
Addenda
Hume's "Treatise"
Hume's Treatise of Human Understanding was a juvenile work. In 1734 (when he was only 23 years old) he published the first two volumes. In 1740 he published the third volume, which included an appendix, which was a compendium with which he tried to make his ideas more accessible.
The Treatise was an anonymous work, which went unnoticed, although its authorship was well known in intellectual circles. Hume acknowledged its authorship in his later works, first in "My Own Life" and later in a note added to the 1777 edition of "Essays and Treatises on Several Subjects".
The Treatise was subsequently rejected by Hume, at least partially. He considered it a failed work. Today, however, it is considered Hume's most important work and one of the most important works of Western philosophy.
In 1748 appeared what is often called the "first Enquiry": An Enquiry concerning Human Understanding, which covered the main ideas of Book I of the Treatise, and his discussion of freedom and necessity in Book II.
In 1751 he published the second "Enquiry": An Enquiry concerning the Principles of Morals, a recasting of Book III of the Treatise, which he considered his best work. When Hume speaks of "Morals" he means everything concerning human nature, and not only ethics, as he himself makes clear at the beginning of his first Enquiry. He calls "moral philosophy" "the science of human nature", to which he wanted to apply the experimental method.
Method of cognitive identification of terms
The method used by Hume consisted of the following. One starts with a term and asks for the idea associated with that term. If no idea is identified, the term has no cognitive content. If the idea exists and is complex, you break it down into simple ideas and identify the original impressions. If the process fails at some point, the term has no cognitive content. If the process is successful, you have an accurate definition of that term.
Hume used this method to show that many traditional terms of metaphysics have no intelligible content.
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Hume, D. An Enquiry concerning Human Understanding. Nidditch, P. N. (ed.). Clarendon Press, Oxford, 1977.
Hume, D. My own life. Cosimo Classics, 2015.
Hume, D. De la moral: tratado de la naturaleza humana. Ediciones Folio, 2007.
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