The search for absolute truth – 4 epistemologies in brief

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THINGS TO KNOW Look at the picture on the right. What do you see? Black and white stripes, distorted and lying crookedly on top of each other?  Well, at least that’s what your brain makes you believe. In reality, the stripes are parallel to each other. No matter whether you already know this optical illusion or not, it poses an existential question: If our brain can deceive us like this, what is still true?

Philosophers have been dealing with the question of absolute truth for two and a half thousand years and have been searching for the best path to knowledge. Over time, four major theories of knowledge have been established, which I will examine in more detail below: idealism, empiricism, rationalism and criticalism. First, however, we need to clarify what truth is in the first place.

Fundamentals and the concept of truth

What is truth? Three theories offer an answer to this question:

  • Consensus theory (lat. “consensus” = agreement): One can speak of truth when people agree on something, there is consensus or an assertion is compatible with related assertions. (Problem: This does not make the statement true).
  • Correspondence theory (lat. “correspondere” = to correspond): One can speak of truth when a statement or thought corresponds with a fact in the world. (Problem: These facts are strongly dependent on circumstances or the state of knowledge).
  • Redundancy theory (lat. “redundare” = to overflow): To speak of “truth” is mostly dispensable, because it is stated that a statement is true. Nevertheless, the terms “true” and “truth” can be used meaningfully.

Furthermore, a distinction is made between subjective and objective truth.

  • Subjective truth is the truth for a single individual. It depends on the individual’s age, experiences and sensory perceptions – i.e. it differs from person to person. Subjective truth is often referred to as relative truth.
  • Objective truth is recognised as universally valid by a group of people (such as scientists) or by humanity. It is often also called absolute (all-encompassing) truth; however, this is problematic because humans can never be omniscient, i.e. achieve absolute truth. The diagram explains this problem in more detail.
absolute truth ans relative truth
The subjective (relative) truths are found in the total mass of (human) objective truth. Absolute truth, however, reaches much further than human beings can comprehend.

 In order to arrive at truth (knowledge), we need different sources of knowledge:

  • The senses perceive impressions of the world (seeing, hearing, touching …) and are a central component of our experiential knowledge.
  • Imagination is the activity of remembering sensory perceptions and their combinations and combining them with earlier perceptions.
  • With the mind, one compares and analyses. One combines concepts and judgements and comes to a conclusion.

Idealism (Plato)

Plato (an ancient Greek philosopher) developed the two-world theory. He distinguished between the world of ideas and the world of the senses:

– He saw the world of ideas as the fundamental reality. It was accessible to the mind and only recognisable through the intellect. This is where the original and pattern images lie, which together form the absolute (objective) truth.

– The images of the ideas are found in the world of the senses, the realm of objects and living beings. The world can only be perceived subjectively, so it contains relative truth.

According to Plato, the whole, absolute knowledge is in the world of ideas. A part of the so-called world soul slips into the human being at birth (also described as méthexis = participation), but the human being forgets this knowledge again. The path of knowledge is thus the recollection of the innate ideas, also called anamnesis. In this process, everyone has to find the knowledge for themselves, others can only put the person on the “right path” of recollection (midwifery = mä(i)eutics).

Example: We perceive the object “tree” in our sense world and remember the idea of the “tree” seen before our birth from the world of ideas. The cognition of what a tree is is therefore a kind of recognition.

Plato distinguished four stages of cognition: presumption (1) and belief (2) in the sense world, and reflection (3) and insight (4, which is achieved only by the fewest and never absolutely) in the mind. He illustrated the path of knowledge in three parables: the parable of lines, the parable of the sun and the parable of the cave. I will now go into the latter in more detail:

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Stage 1: Deep down in a cave, people are bound for the rest of their lives. They can only look straight ahead at a wall where they see shadows passing by. Knowing nothing else, they think these shadows are real and the sounds they hear are their voices. They do not see that there is a fire burning high above them, that the shadows are really coming from objects being carried by people behind a great wall, and that the sounds are coming from the voices of these people.

Stage 2: If a person is freed and forced to climb the wall behind him, he will at first be blinded by the fire and unable to see what the cave is really like. He is confused and considers the real objects less real than the shadows he has known all his life. In time he gets used to the light and recognises the objects as true. But he feels visibly uncomfortable.

Stages 3 and 4: So he has to be forced to climb further and leave the cave. Again he is blinded by the brightness. He soon recognises rivers, mountains and plants. And he recognises the sun as a source of light and that the reflection of the tree is only an image, not reality. If he now returns to the cave to free his fellow men, they will laugh at him, prefer the familiar to knowledge and possibly kill him.

What does the allegory of the cave want to tell us? Taking the step from the world of the senses (the cave) into the world of ideas (outside the cave) is hard and only very few will take it. Those who have made the step (here Plato refers to philosophers such as Socrates, who perished through the cup of hemlock) will almost certainly not be believed.

Empiricism (John Locke and David Hume)

In contrast to idealism, empiricism believes that the appearing objects of our world are real. According to the motto: “There is nothing in the intellect that was not previ­ously in the senses”, empiricists derive all knowledge inductively from the experiences of the senses.

According to John Locke (1632-1704), man at birth is initially a blank slate (tabula rasa) who comes to knowledge through sensation and reflection.

  • Through sensation he experiences externally perceptible impressions/objects. From primary qualities (objective impressions) and secondary qualities (subjective impressions), man creates simple ideas, which can become complex ideas through the intervention of the subject (combination of simple ideas with own experiences).
  • With the help of reflection we perceive inner impressions. We sense, so to speak, inner processes of our mind, for example, whether we think, compare, conclude, doubt or believe.

For Locke, the term “experience” refers to knowledge gained through contemplation, perception and sensation as the basis of knowledge. Locke also divides certainties into the demonstrative (based on demonstrable facts), the sensitive (based solely on sensory perception) and the intuitive certainty (which is based on immediate insight).

David Hume (1711 – 1776) divided objects of human thought and research into relations of ideas and matters of fact:

  • Relations of ideas: e.g. mathematics, high certainty (corresponding to demonstrative certainty), to be found out by mere, objective thought activity, not to be sensually perceived, valid without having to exist in the external world.
  • Matters of fact: conclusions that are never certain and are always conceivable otherwise because we cannot prove anything, such as “Will the sun rise again tomorrow?”

He referred to the experience of mankind as the middle link between these two. In this context, Hume expanded Locke’s concept of experience to include qualities that remain hidden from our senses and our intellect and that we can only ascertain through experience. Thus he spoke of a sense of expectation that sets in – according to the law of causality – when certain impressions occur regularly (cause-effect relation).

Rationalism (René Descartes)

Contrary to empiricism, rationalism primarily invokes the intellect as the source of reason. René Descartes (1596 – 1650) wanted to derive knowledge exclusively with the intellect using deductive methods from premises. This was possible with the help of ideas innate to humanity from nature – he included the idea of infinite substance (God), finite and thinking substance (human mind) and finite and extended substance (matter). Descartes separated the world into:

  • material world: “Res extensa” as the physical, finite world (the external).
  • non-material world: “Res cogitans” as the thinking, infinite mind (the inside).

He described cognition thus: At the beginning of life, man is free from all cognition and misguided by prejudices. The path to doubt-free cognition leads through methodical doubt:

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  1. radical doubt: being aware of one’s fallibility and fundamentally doubting everything (perception/thinking/existence).
  2. analysis: breaking down problems into small, simple sub-areas
  3. construction/systematisation: structuring the areas in order to then solve the problem from the simple to the difficult
  4. verification: are there contradictions? is everything complete?

Descartes also noted that there seems to be no effective criterion for determining whether one is currently awake or dreaming or has fallen prey to other illusions. Rational knowledge is therefore in principle doubtful (dream argument). As the only certain knowledge, the rationalist came to the conclusion: “I think, therefore I am” (because that which thinks cannot exist at the time it thinks).

He saw the proof of God’s existence in the mere existence of the divine idea in our consciousness. The idea of God could come neither from outside nor from consciousness, because it contained the absolute truth. God himself had to have given us this idea. According to Descartes, this proved the world as complete and knowledge as the highest human faculty (proof of God).

Reflection of empiricism and rationalism

While empiricism claims that all knowledge stems from experience with sensual perceptions as its basis, rationalism seeks knowledge in reason. In doing so, it even borrows in part from Plato’s theory of ideas from idealism. One could say: in rationalism, Platonic recollection becomes the realisation of ideas that were originally already implicit. It is different in empiricism:

“The mind does not seem to me to have the faintest glimmer of any ideas which it does not receive from one of these two sources [sensation and reflection].” (Translation of an excerpt from: John Locke. In: Ekkehard Martens (ed.): Ich denke, also bin ich, C. H., Beck, Munich 2000, pp. 146 – 149).

If one applies the two epistemologies in science, one arrives at two basic principles:

covid 19, coronavirus, covid, Zelle, pandemic, corona virus, Produkt, Labor, Chemiker, Bedienung, Wissenschaft, Forschung, Laborausrüstung, Chemie, Apotheke
  • Inductive research (empiricism) is concerned with making a general statement with the help of an individual case. In this type of research, one tries to derive conclusions for the generality from an observed event.
  • Deductive research (rationalism) is about drawing conclusions from a general statement to an individual case. In other words, one tries to test a generally valid theory with a direct example.

Example: research on the corona virus:

  • inductive: animal experiments provide basic findings in corona research -> findings for knowledge for humans
  • deductive: Investigation of findings about COVID-19 predecessors: diseases and vaccines, thus conclusions about the current virus.

The criticism of empiricism can be roughly summarised as follows:

  1. sensory illusions are possible and sensory data are limited.
  2. according to the induction problem, there is no unlimited logical validity and no certain knowledge (are all birds black because one is?).
  3. empiricists offer no explanation of causes, they only observe events (causality problem).
  4. there is the possibility of false basic ideas and naturalistic fallacies.

Rationalism tends to be criticised for the all-determining doubt and eternal uncertainties that never allow for a definitive conclusion.  The existence of innate ideas is strongly debated; moreover, reason not infrequently arrives at several possible conclusions that lack any closeness to reality.

The attempt to combine both schools of thought and thus balance the respective disadvantages has often been made. An example of this would be Kant’s “Critique of Pure Reason”.

Criticism (Immanuel Kant)

Immanuel Kant (1724 – 1804) first made a basic division of judgements:

  • Analytical judgements can be concluded solely from thinking, i.e. the analysis of a concept (and its properties), e.g. “bachelors are unmarried.”
  • In synthetic judgements, several concepts must be brought together (composition of statements -> addition of experience), e.g. “Yesterday the street was wet.”
  • Judgments a priori can be justified without the addition of experience, e.g. “The sum of the interior angles in the triangle is 180°.”
  • Statements a posteriori need experience, e.g. “The orbital period of the moon around the earth takes 28 days.”

Bringing these distinctions together, he came across the following four cases:

  • Synthetic judgements a posteriori correspond to the empiricists’ induction.
  • Analytical judgements a priori make use of the deduction of the rationalists.
  • Analytical judgements a posteriori are not meaningful.
  • Synthetic judgements a priori are controversial: rationalists think they exist, empiricists claim the opposite.

But how did Kant himself answer the question? He said “yes”. In principle, synthetic judgements a priori do not exist, except for space, time and causality as innate ideas of thought. Kant described this idea in more detail in his “Critique of Pure Reason”. His main statements were:

File:Kant Kritik der reinen Venunft 1781.jpg - Wikimedia Commons
Immanuel Kant: “Critique of Pure Reason”
  • the necessity of experience and mind for cognition
  • the dependence of our cognition on innate ideas -> beyond this we cannot think

Immanuel Kant wanted to establish the structure and limits of human cognition. In his work, he focused on the subjective perception/knowledge of human beings. And he came to a significant conclusion: “It is not the perception that depends on the nature of the object, but the object that depends on the nature of the faculty of perception.” This reversal of our understanding of cognition is also known as the “Copernican turn”.

In the starting point, Kant agreed with the empiricist Hume that we owe our knowledge to sense perceptions; but important conditions for how we perceive the world also lie in our reason. Accordingly, there are certain conditions within us that help determine our perceptions of the world. He called these conditions “forms of knowledge a priori (before all experience)” and distinguished the “forms of perception” (time and space) from the “forms of thought” (the 12 categories of pure understanding). This gave rise to his so-called “transcendental philosophy” (transcendent = lying before all subjective experience and making the knowledge of objects in itself possible in the first place).

In concrete terms, this means that although the senses provide the material for cognition by perceiving appearances of things, the things themselves are not recognisable because we automatically and inevitably impose a structure on them with time and space (transcendental aesthetics). The mind must now form judgements from the experiences in order to arrive at knowledge. To do this, it connects objects of perception with concepts by applying the 12 categories of pure understanding. Here, the thing in itself is also not recognisable (transcendental logic). In this sense, time, space and causality are, according to Kant, primarily properties of our consciousness, not of the world in itself.

Because of this distortion of reality, Kant sees it as necessary to establish principles for the correct use of reason. According to him, reason must not be purely speculative, but must always be used practically (-> 4 Kantian Questions). Philosophy should be based on science and opposites (e.g. rational – empirical).

Final note: This article was written in preparation for my oral examination in ethics. General tips for the oral exams can be found here.


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