Rational Thinking is a development of mind above the Reasoning-ability. It is that stage of development of brain when a person starts evaluating which one among so many reasons is the appropriate one for circumstances which are in the question. To a simple question, ''why should we keep on the left side of the road, when driving'' , the number of reasons (such as ''Because there is a law'', ''because to give way to the opposite traffic'', ''because the steering wheel is on right side of car'', etc) , Rational Thinking is the development stage of brain when it begins to Judge which is applicable reasoning for the circumstances which are in question.
The basic ability of human brain , if it is born 'normal'(without any birth defects) is called Cognitive Abilities. a small child can be seen displaying the development of Cognitive Abilities as he grows from infancy to toddler to child stage. From the cognitive Abilities , the brain launches into Mental abilities when it is able to think little more advanced - using the skill of Imagination, Time scale, and more .
From Mental Abilities , the Brain builts up the Reasoning Abilities when it starts looking for the underlying theories for the events happening around him.
Rational Thinking arrives when the Brain starts to Judge which of the so many reasoning is accurate, appropriate and which is not.
The progress of brain is not a granted event. Which means, it cannot be stated that it is going to happen so in every person who is born with a normal brain. The cultural factors play a role, affect the Judging abilities of person when a person fails to detach himself from the world in order to take a bird eye view of the circumstances around. He , then , fails to reach the Reasoning Abilities, when he starts accepting the Reasoning ''because there is a law'' as the sole explanations for events happening around him. He avoids to question the rational of the law itself . reading and writing skills become a necessary tool to reach to the stage of Rational Thinking. To discuss the numerous reasoning , and then to choose the appropriate ones is no easy guess work. It requires a more laborious work to making evaluation of each of these reasonings.
where should we place the Intellectualism in the Brain Abilities development chart?
In my opinion, Intellectualism is an ability parallel to Reasoning Ability. The difference being that Reasoning Ability is for measurable things (quantitative) and Intellectualism is for abstract things (qualitative). Making evaluation of abstract things such as Beauty, Emotions, Likeness /fondness, hotness, coolness, et al - will require brain to develop a different neural pathway. These parameters are severely connected with the environment around each individual. While one may not disagree so much about what is the minimal standard for beautiful-ness, the higher side of evaluation "who is more beautiful/ most beautiful" is immensely different.
The lower side of judgement has been worked by a broader parameter, while the higher standard of judgments is affected by very narrow , personalized factors.
Intellectualism is the search of quality. Reasoning Ability is working with the quantifiable things. A piece of literature, a book, a poem - cannot be judged with the help of Reason. As is done with the quantifiable things, for the abstract things of Intellectualism the judgments of person improve as he undertakes the Criticism. Intellectual judgments improve if a person exposes himself to someone else's criticism. 'Criticism', in the Brain abilities of Intellectualism , is synonymous to "Data Analysis."
The higher brain capacities of judgement cannot be built unless these lower foundation abilities are improved or mastered.