As they grow, children are able to engage in a more refined form of mental activity. They now begin to focus, not merely on the forms of things, but on what those things do or how they behave. This is an advance on mere sensation. The child is now making generalizations of forming conclusions or laws about those images that have come into their minds by way of the sensory level. Swedenborg’s term for those generalizations is scientifics. Although the children aren’t yet aware of it, by drawing conclusions based on their sense perceptions they are being little scientists, using the scientific method (Secrets of Heaven, Section 5774:2). They conclude scientifics. This opens the middle level of their natural mind, called the middle natural. This provides a basis for the rational level—the highest level of mental activity in our natural mind.
The two lower levels of our natural mind—the sensory and the middle natural—can be opened simply by experience, by receiving sense impressions and by drawing conclusions from them. Even an atheist can have those two levels opened. But something more is needed to open the rational level, the highest level of natural mind.
from The Hidden Levels of the Mind, Swedenborg’s Theory of Consiousness by Douglas Taylor