The art of argumentation has many components. However, the most important, connecting, as in an optical focus, all other components, is the ability to reason, to support the put forward positions with convincing arguments. The validity of knowledge is one of the essential requirements for theoretical thinking. The concept of substantiation is central in the theory of knowledge in general and in the methodology of scientific knowledge in particular. Each specific scientific discipline historically develops its level of accuracy and evidence. Nevertheless, no matter what field of knowledge a particular proposition belongs to – whether it is about mathematics, physics, or ethics – it is always assumed that there are sufficient grounds under which these propositions are accepted or considered authentic.
The validity requirement is presented in a somewhat weakened form and to practical thinking. Here, the ideas put forward must be supported by sufficiently clear and convincing arguments, although the very nature of the argumentation within the framework of practical thinking changes significantly. The law of sufficient reason is one of the basic general logical principles, according to which, in the process of reasoning, any judgment is considered authentic only if a sufficient reason for its truth is given (Amijee, 2021). The requirement of justification applies to everyday knowledge as well. For all its inaccuracy and amorphousness, the latter must also be based on specific, relatively reliable foundations.
According to Leibniz, everything that exists has sufficient grounds for its existence. Because of this, no phenomenon can be considered accurate, and no statement is true or just without specifying its basis. If all necessary truths are based on the logical law of contradiction, Leibniz believed, the principle of sufficient reason is the premise of all factual and accidental truths. However, the characterization of the latter given by Leibniz needed to be clarified, and attempts were soon made to reduce the requirement of sufficient reason for the consistency condition. In the future, Leibniz’s idea will be understood in different ways. In particular, the German philosopher of the XIX century. A. Schopenhauer interpreted it as a position about the necessary relationship of each phenomenon with all other phenomena; time, space, causality, and the foundations of knowledge and behavior turned out to be diverse forms of manifestation of the fundamental interdependence of phenomena (Amijee, 2021). The requirement of sufficient reason usually extended to all judgments, but sometimes an exception was made for judgments of direct perception, axioms, and definitions. It was believed that axioms, definitions, certified judgments of direct experience, and inferential judgments, already justified by evidence, can be a sufficient reason.
The law of sufficient reason does not say anything about the connection between a sufficient reason and the thesis being proved, which can differ depending on the proof’s form and the type of inferences included in it. It requires only the necessary following of the truth of the thesis from solid grounds (Amijee, 2020). The law is violated if the proposition being proved does not logically follow from the arguments or if the latter contains false propositions. Since “insufficient reason,” that is, a reason from which a justified proposition cannot be logically deduced, does not make sense to call a reason, the law of sufficient reason is often called simply the principle of reason.
The law of sufficient reason contains several prescriptions: all premises of reasoning, inference, proof, and conclusion must be justified; if any judgment is justified, then it is permissible to use it in proof without reproducing its reasons but only implying them (Lu-Adler, 2020). This prescription also allows the use as premises of synonymous provisions or those whose justification is a consequence of proven or proper provisions. In addition, justification is considered to be any truth characteristic of a judgment or a false judgment, a probabilistic judgment. Finally, in justifying judgments, one should distinguish between logical justification: the relation of the conclusion of a logical consequence, and factual justification.
In the subsequent development of logic, the law of sufficient reason was understood as purely logical or a logical-ontological principle. In the 18th-19th century, a tradition developed in formal logic to include it among the four so-called basic thinking laws, the law of identity, the law of contradiction, and the law of the excluded middle. Along with this, objections have long been raised against understanding the law of sufficient reason as a special logical law, similar to the other three laws. These objections gained credibility in connection with the development of mathematical logic when it became clear that the very problem of strong reasons, which was touched upon by traditional logic in connection with this law, was interpreted superficially without taking into account the systemic nature of scientific knowledge and the dynamics of its development (Amijee, 2020). The subsequent development of logic showed that the law of sufficient reason has an exclusively substantive nature and cannot be formalized: unlike the laws of identity, contradiction, and the excluded middle, it cannot be represented as a formula of any logical calculus. It is a general logical principle, coinciding with the original ideas of the logical theory of proof, especially deductive proof. In this sense, those refinements of the concept of proof developed in mathematical logic can be regarded as a refinement of the law of sufficient reason. Although the traditional law of sufficient reason is limited in the indicated sense, it nevertheless has a broad rational content since it characterizes one of the essential features of logically correct thinking – evidence.
Emily Du Châtelet is known in scientific circles as a mathematician who provided the translation of Newton’s Principia Mathematica of Natural Philosophy from Latin into French. However, she made a much more significant contribution by integrating Newton’s mathematical reasoning into the system created by Leibniz. Her understanding of this category occurs in terms that differentiate “understanding why” and “understanding how,” which, as a result, makes some explanations either good or bad (Wells, 2021). According to Leibniz, the causality of any statement may be unknowable for humanity as a whole; researchers do not even set such a goal. Du Châtelet, on the other hand, differentiates practical explanations according to well-understood criteria, with the result that her treatment is neither overly demanding nor trivial.
David Hume drew a skeptical conclusion from the empiricism of Bacon and Locke. Following Berkeley, he believed that since experience consists of the perception of something unknown, all possible objects of knowledge are only our perceptions. Depending on their liveliness and strength, Hume divided these perceptions into impressions, sensations directly experienced by a person, and ideas or representations. Hume considers ideas to be more or less vivid copies of sensations created by the imagination and reason from the material supplied by the senses. According to Hume, the transformation of sensations into ideas is due to the ability to think to connect or associate sensations with each other according to the principles of similarity, contiguity in time or space, and the relationship of cause and effect (Anderson, 2019). According to Hume, the entire content of human consciousness is either pure relations between ideas, or the facts of experience, in which sensations are always mixed with ideas created by us.
Since the effect is quite different from the cause, it cannot be intuitively seen in the cause and logically deduced from it. Hume convincingly shows that no phenomenon of causality can be known a priori, i.e., initially, immediately, without any experience. Before establishing a causal relationship of facts, a person must, by all means, be convinced of it by experience – repeatedly experience it a posteriori, i.e., based on the following reason (Anderson, 2019). Belief in the existence of a universal and necessary connection between phenomena saves people from complete skepticism and agnosticism, i.e., disbelief in the recognizability of the world, allowing them to act in the world of external nature and in a society of their kind to behave like moral beings. Thanks to this practical instinct, all the empirical sciences, as well as religion and philosophy, exist.
David Hume favorably stands out among many philosophers interested in the problems of epistemology. The main goal of Hume is the construction of ethics based on knowledge of the interaction of man with the outside world. Nevertheless, the Scottish empiricist is remembered and honored precisely for his epistemological theory. Hume is convinced that causality as a relation between objects is not perceived directly, being only an idea. The basis of causality is the belief in the regularity of events based on the habit of observation. Hume’s awareness of this circumstance also determines the transition from the “Treatise” to the “Investigation,” which is accompanied by a refusal to consider causality in ontological terms and a transition to the analysis of causal statements. Perhaps, in general, “Investigations” can be characterized as a turn from reality to language, from the origin to the structure of the idea, and from ontology and psychology to epistemology (Mills & Mills, 2020). Hume then asks what causes this automatic transition from cause to effect. He is sure that neither reason in itself nor reasoning as such, but something else determines this ability of the soul since reason can never convince a person that the existence of one object contains the existence of another; therefore, when researchers move from the impression of one object to the idea of another or the belief in this other, it is association or habit, not reason, that prompts them to do so (Pallies, 2019). From these words, it follows that reason is a secondary phenomenon.
A somewhat abstract manner of reasoning characterizes Hume’s philosophy. He refuses to reveal the causes, that is, the sources and origin of the particular mechanism that determines the reliability of human sensually practical experience. In An Inquiry Concerning the Human Mind, the scientist constantly refers to “human nature” or to each person’s individual experience. Such a technique prevents any systematization in such matters. Another essential feature of Hume’s philosophy is rejecting the principle of induction applied to causality (Mills & Mills, 2020). Of course, this meant a deviation from pure empiricism and the scientist’s recognition as a skeptic in the matter of knowledge. The share of skepticism here is not at all outstanding because the scientist only partially accepts experimental knowledge. Nevertheless, Hume’s philosophy posed before subsequent thought the critical question of the complex objective structure inherent in individual experience; it allowed, for example, Kant to recognize the sensory experience as a complex sensory-rational formation with the inclusion of a priori, i.e., universal, forms (Lu-Adler, 2020). Drawing a parallel with the principle of sufficient reason as understood by Leibniz and Du Châtelet, Hume’s causality is of a somewhat different nature and is introduced into his teaching for other purposes.
It is also worth noting the different nature of how Leibniz and Du Chatelet look at PSR. Speaking of causality, Hume and Leibniz are closest to each other. The latter often indicates in the description of his works that the reason for the reliability of empirical statements may even be unknowable in general (Pallies, 2019). Hume, in turn, speaks of a similar idea: a person is guided by associations or habits but not by reason, while natural causes always elude researchers. Du Chatelet tries to get out of this circle of judgments by approaching the consistent creation of criteria for reasonable empirical justification. In fact, the PSR postulates a connection between events, but the nature of the connection and Hume’s teaching does not undermine the new definition of causality.
First, Hume focuses more on individual experience through the context of human cognition. His concept of habit is a specific mechanism for synthesizing knowledge and cognition, which has developed in individual experience during social practice. Given the fact that for each person, such an experience will be different, then the habit or associativity underlying causality will be different. The problem of causality has integral significance for philosophy and science. After all, in Hume, the basis of new empirical science is a theory of knowledge, itself based on experience. In this case, the primary source of knowledge is some causal connection; the question of the source of knowledge is also the question of the cause of our ideas. Therefore, the theory of knowledge is as consistent as it can solve this problem. Hume does not find the source of knowledge within narrowly understood human nature precisely because it is not there. Knowledge and consciousness are sources outside the human body, which is in active interaction with the world and other people. Reality is a product of everyday consciousness, in which a person is convinced of the possibility of knowing the world and that the facts of his consciousness somehow correspond to the elements of reality. Consciousness, taken as the subject of philosophical analysis, does not allow a reasonable exit beyond its limits, simply excluding any ontological problems from consideration.
Secondly, the problem was directly addressed by Du Chatelet, who brought her comments to Newton’s work to adapt and understand the mechanisms of cognition, including causality, in isolation from human perception. Leibniz, on the contrary, had his vision of ontological causality; however, introducing the religious categories of God and pre-established harmony and the principle of sufficient reason in a critical sense was isolated from these scales. As a consequence, the understanding of the principle instead leaves Hume’s causality untouched, and vice versa, since the connection between events is described mainly from the context of human cognition and differs in these mechanisms but not in its essence.
References
Amijee, F. (2020). Principle of sufficient reason. In The Routledge handbook of metaphysical grounding (pp. 63-75). Routledge.
Amijee, F. (2021). Explaining contingent facts. Philosophical Studies, 178(4), 1163-1181. Web.
Anderson, J. (2019). Hume, Causation and Counterfactuals. Humanites Bulletin, 2(1). Web.
Lu-Adler, H. (2020). Kant and the Principle of Sufficient Reason. The Review of Metaphysics, 74(3), 301-330. Web.
Mills, T., & Mills, F. (2020). Correlation, causation, and David Hume. Australian Mathematics Education Journal, 2(4), 44-48. Web.
Pallies, D. (2019). Why humean causation is extrinsic. Thought: A Journal of Philosophy, 8(2), 139-148. Web.
Wells, A. (2021). Du Châtelet on Sufficient Reason and Empirical Explanation. The Southern Journal of Philosophy, 59(4), 629-655. Web.