Formal Rational: Internal
We are now switching to internal development which - relative to external - is dynamically negative. With reference to our cutting the cake into four slices this could be written 1-(1/4).
Thus correctly understood formal rational development at an internal subjective level takes place in negative fractional dimensions.
What this means in practical terms is that one now develops the ability to analyse internal subjective concepts.
Again this stage will have two overlapping aspects. Firstly one develops the ability to relate emotionally to reality in a more refined general manner (without being unduly influenced by immediate feelings). In other words one is enabled to discipline one's emotions in a more mature fashion. However once again - though a very necessary component of civilised behaviour - as feeling operates now increasingly under the influence of reason, this may involve much repression.
The other aspect is more directly cognitive - whereby one develops the capacity for right judgement in terms of formulating abstract ethical rules. Legal principles and moral philosophy would exemplify this capacity.