The complexity of the English language is a level of complexity within a relatively simple framework. The scale of the vocabulary and the flexibility of statement construction disguises an underlying systematicity which is built from very few components.

At the top level there are 5 statement components. These components can be formed from 4 types of component and organised into 3 statement types.

At the next level down in the structure there is a significant level of flexibility but the potential complexity is kept manageable by being constrained within this framework. The simplest version of the language and the most complex are contained within the same high-level structure. This means that children who have just learned to talk speak the language within the same structure as the most highly proficient adults. 

There are three paths from the simple version to the most complex. The first path is through the accumulation of qualifications and conditions. This can be done by various means such as adding adjectives and adverbs, prepositional phrases and relative clauses. The second path is through the use of more complex structures such as lists and pairs, infinitives, gerunds and verb chains. The third path is through the accumulation of the lexicon of every domain that we come into contact with.

There is a theory in linguistics that proposes that there is something like an innate grammar. The argument is that native speakers don’t accumulate enough experience o work out what is correct and what isn’t through trial and error and that therefore there must be some internal schema against which sample of language are being compared.

However, if my analysis is correct, it indicates that what is learned as a child is actually quite simple. The complexity of language, its infinite flexibility, is a broadening out of the possibilities within essentially a simple framework. Native speakers learn as children the structure of the language in its entirety but they do not learn how to exploit the full range of possibilities. The full range of possibilities within the system is what is learnt over time.