onsistent use and atrophy with lack of use.
In conclusion, theory Y, which asserts that the elderly’s intellectual capacities remain stable throughout their life-span, is as valid as theory X, which claims that intellectual capacities disappear with age. In fact, it is not age itself that brings a decline in intellectual capacities, but the lack of exercise due to the lack of possibilities for elderly people to exercise their intellectual faculties. From this perspective, nothing prevents the elderly from developing their intellectual capacities throughout their lives.
With theories X and Y, we see that researchers do not agree on the decline of intelligence in seniors because they do not define intelligence the same way. Indeed, research shows that intelligence can be defined from a quantitative or qualitative perspective, which we will present as quantitative or qualitative intelligence.
3.2. Definitions of Intelligence
3.2.1. Quantitative Intelligence
Indeed, in theory X, researchers assume that all aspects of intelligence that increase eventually decrease. With the “Weschler’s Adult Intelligence Scale (WAIS)” test, Weschler  demonstrated that old people are less intelligent than young people and that intelligence increases until age 30, remains stable for 10 years, and begins to decline around 40 years old. Miles and Miles  and Jones and Conrad  confirmed this hypothesis by showing that seniors obtain poorer results when they are subjected to intelligence tests that require completing a task in the shortest time possible.
While improving intelligence tests allowed for better interpretation of results, it did not allow us to address the problem that not only there was no agreement on a common measure, but also again that intelligence was defined differently. According to this school of thought, the definition of intelligence is summarized as the capacity to do well on an intelligence test . It is presented as a quantitative entity, thus measurable. “Tests have transformed the notion ... of intelligence: ... it has become a unique quantifiable entity .”
3.2.2. Qualitative Intelligence
Yet, many researchers who criticized the tests’ statistical methods wanted to present intelligence as multifaceted and qualitative rather than a unique and quantifiable entity.
The distinctive contribution of Terman  at the inception of this new orientation in the definition of intelligence, is presenting intelligence as the capacity to learn, to reason, to elaborate concepts, and to play with abstractions. Botwinick  sees intelligence as multidimensional and Horn  distinguishes two dimensions, fluid intelligence and crystallized intelligence. Baltes and Shaie  and Willis and Baltes  present fluid intelligence as being comprised of faculties that are independent of culture, whereas we find in crystallized intelligence the aptitudes acquired through education and culture. This type of intelligence is characterized by plasticity, allowing individuals to assimilate their own culture’s collective intelligence.
4. Qualitative Intelligence and Basic Forms of Dialectical or Post-Formal Thought
4.1. Elementary Forms of Piaget’s Dialectical Thought
Piaget  portrays qualitative intelligence as the capacity to adapt to one’s environment. Piaget  presents this plasticity as being rooted in a dialectical conceptualization of intelligence, which characterizes the elder’s thinking style.
The reader will be surprised by our comments on Piaget’s genetic epistemology and Marx’s dialectical theory. Indeed, “Seldom has genetic epistemology been considered as a dialectic of knowledge. Piaget’s own references to this aspect of his theory are scattered and indirect .”
Moreover, numerous critics claim that Piaget cannot be assimilated into a Marxist tradition and that genetic epistemology cannot be compared to Marxism as it handles this philosophy in a completely different way.
Yet, this definition of dialectic proposed by Piaget. “There is dialectic when two systems, thus far distinct and separated but not at all opposed to each other, merge into a new whole, the properties of which surpass the originals, and sometimes by a considerable extent,”  is eerily similar, according to Garcia, “to the characterization of dialectic as a theory of is eerily similar, according to Garcia, “to the characterization of dialectic as a theory of opposites.” opposites.” The word opposites, he adds, should not be interpreted “in the exact sense of formal logical contradiction.”
In addition, Piaget’s definition of dialectic assumes that the two independent systems, which appear as absolutes and give birth to a new whole, must undergo a “revitalization” process to build a larger system than the previous two. Thus, in Piaget’s definition, we have the two principles that constitute a dialectical thought, namely the principle of contradiction and the principle of revitalization of everything. However, it must not be presumed that dialectic intervenes at every step of cognitive development. In the analysis of logical-mathematical thought, it seems:
“Once a theory has been established, it operates in a purely deductive (or ‘discursive’) manner. And deduction as such is not dialectical ”.
This is why scientists are reluctant to include dialectic in scientific theories but prefer to function in a deductive manner in their “problem solving.”
Formal or dialectical thought Consequently, it seems possible to claim that:
“Piaget belongs—whether he likes it or not—to a line of thought ... of the most important dialectical school of our time. [Hegel, Marx and Lenin] ... Genetic epistemology has created (or has begun to create) the psychogenetic and sociogenetic research program that Lenin pointed out as being necessary ... ”
4.2. Choice of Formal Thought in the Work of Piaget
However, we must admit that, although Piaget presents basic forms of dialectical thought in the child’s cognitive development, researchers agree that his work focuses mainly on the development of logical-mathematical or formal thought. We have to wait until John M. Rybash’s writings, which synthesize the literature on the essence of post-formal thought, namely dialectical thought, to understand that although it is found in young people, it is above all the prerogative of elders. Genetic epistemological research shows that older people’s thinking style is qualitatively different from the characteristics of Piaget’s formal operations. Those thinking styles that we only find in seniors are post-formal in nature. In the next section of our article, we will introduce the characteristics of this post-formal thought.
5. Qualitative Intelligence and Rybash’s Fundamental Principles of Dialectical or Post-Formal Thought
Although Rybash was able to present a synthesis of adult thought in a single volume, we must acknowledge that Basseches [35-37] was the foremost scholar in the area of dialectical thought.
He is the one who published the most research in this field and who emphasized the four aspects of post-formal thought. Indeed, his research led him to demonstrate that post-formal thought is based on:
a) The contradiction and relativity of knowledge;
b) The development of meta-systemic reasoning or reflective thought;
c) The “problem finding” rather than “problem solving”;
d) The development of dialectical thought.
In the following portion of the text, we will examine each of the points listed above to explain their originality.
5.1. Contradiction and Relativity of Knowledge
The principles of contradiction and relativity are notions that were originally brought to us by Marx and Einstein. With his principle of contradiction, Marx has familiarized us with the idea that an antithesis opposed every thesis, which together formed a synthesis, that is to say a new reality coming from the thesis and the antithesis, but which had nothing to do with these items anymore. This position, applicable by Marx in sociology, brought deep instability as change was any reality’s dynamic element and nothing could be taken for granted. We have already developed this Marxist principle in our analysis of Piaget’s thoughts.
Yet, when we apply this principle of contradiction to our development of knowledge, we are forced to acknowledge the: “… necessary subjectivity to describe relativistic thinking within the area of the interpersonal relations. Necessary subjectivity means that interpersonal reality is characterized by mutually contradictory frames of reference .”
In that context, researchers discover that the reciprocal contradiction of frames of reference brings a kind of knowledge asymmetry or imbalance that no observer is able to properly explain. “It was the detection of a type of asymmetry that compelled Einstein toward the development of his theory of relativity .”
As we have just shown, this contradictory and relativistic nature of post-formal thought applies not only to pure sciences such as physics but also to social sciences like psychology.
5.2. Meta-Systemic Reasoning
We must conclude that this type of thinking brings us to a reasoning that is other than logical, a meta-systemic reasoning, typical of reflective thought. This reasoning does not imply knowledge of a system’s elements, but knowledge of operations that apply to different systems, thus, that goes beyond the systems to observe their interactions. This ability to create meta-systemic operations endows people with the logical capacity to understand the legitimacy of value systems other than their own. These qualitative adaptations in adult thought are related to meta-ethical changes that emerge at this stage of life. Kohlberg  provides a convincing example of this in his longitudinal analysis of moral reasoning from adolescence to adulthood.
5.3. Problem Finding
Arlin  compared the characteristics of Piaget’s formal thought with the characteristics of post-formal thought that we just covered. Her analysis shows that formal thought, the thought associated with formal operations, is mainly related to problem solving from a logical perspective that evolves in a known system, the interrelations of which we can control. However, her study shows that post-formal thought is essentially related to solving tasks, linked to presenting a problem within its context and in all of its dimensions (problem finding).
Yet, in her study, Arlin asserts that, for problem finding, a person must be capable of problem solving. As a result, formal thought or the capacity to develop Piaget’s formal operations is a necessary prerequisite to access post-formal thought or the capacity to create post-formal operations, that is vast intellectual operations on the principles of the contradiction and relativity of everything. This is why she suggests adding a fifth post-formal stage to Piaget’s four stages.
5.4. Development of Dialectical or Post-Formal Thought
In the previous paragraphs, we saw that post-formal thought functions through operations based on the principles of contradiction and relativity, whereas formal thought functions through logical-mathematical operations. While formal thought is termed logical thought in Piaget’s theory, Rybash  uses the term dialectical for post-formal thought. Many researchers, such as Sinnott and Guttman  Basseches [35-37] and Kramer and Woodruff  have studied the development of dialectical thinking in adulthood. Even though these researchers used different conceptual and methodological approaches to study dialectical thought, they all conclude that this thinking style falls within the constructivist tradition, meaning that operations are created by individuals and are not mere copies of reality.
Moshman  has been the one who most insisted on the constructivist nature of all knowledge. He argues that Piaget’s theory and Piaget’s own thinking fall within a dialectical constructivist thinking paradigm. From that perspective, Moshman’s work analyzes the assertions we expressed earlier in the paragraph on Piaget’s basic forms of dialectic in depth.
Although dialectical thinking operates differently from formal thinking, we hypothesize that there exists, after the formal thinking stage, a fifth stage of post-formal thinking, as Piaget had already studied its basic forms and would have concluded the same thing, had he had time to do so. However, we cannot credit Piaget with this notion, as we are simply hypothesizing. We can only state that post-formal thought constitutes a thinking style peculiar to adult thinking.
In this article, we have demonstrated that the human brain has an infinite regenerative capacity and that even if we lose brain cells with age, the brain compensates for this loss and creates other synaptic connections that allow it to continue having enriching intellectual activities throughout the life-span.
Based on this observation, with his theories X and Y, Jones demonstrated that, depending on whether we define intelligence in a quantitative or qualitative manner, we have a pessimistic or an optimistic outlook on the possibility of learning in old age.
While it is true that sensory functions, speed of processing, and long-term memory decline with age, there is evidence that vocabulary, semantic knowledge, and wisdom all increase with age. These cognitive functions are very important in the learning experience of the elderly, as we have shown in describing post-formal thought. Thus, seniors must take advantage of this post-formal thought in confronting the intellectual challenges preventing them from wanting to continue learning throughout their lives, and depriving them of an excellent tool to counter degenerative brain diseases.
Indeed, research shows that intense and consistent intellectual stimulation may prevent or at least limit the decline of cognitive functions. It is now established that every step of our life corresponds to a specific learning experience in our personal development that depends on our biological, psychological, societal, and personal maturity. Thus, for the elderly, with the development of post-formal thinking, the ideal goal of learning is the acquisition of wisdom. “Thus, wisdom is not simply for wise people or curious psychologists; it is for all people and the future of the world .”
From that perspective, life experiences and an elder’s personality are more important in the functioning of post-formal or dialectical thinking than the pure intellectual logic of formal thinking to acquire wisdom, wisdom being, as mentioned before, the aim of adult learning. Indeed, wisdom makes elders aware of themselves and of their own identity by fostering a comprehensive conception of human development in its limited, intellectual, social, and genetic aspects. “Wisdom, a notion that the university had transformed to science in their theology and philosophy faculties, finally finds its true identity in action, in the education faculties .”
While researchers in the education sciences have thus far neglected the aspects we developed in this article, we hope that in the future, it will be possible to develop research in this field in universities. This would allow researchers to further knowledge on the psychology of learning in the elderly to carry out a university program focused on the acquisition of wisdom.
Note: All quotations in italics were originally in French and were translated herein by the authors to make the article easier to read. The authors are the only ones responsible for these translated quotations.