When we order our words, we order our thoughts.
The mind uses networked non-sequential processing of ideas, meaning that we often think about more than one thing at the same time (or at least move back and forth between subjects). Writing, however, requires a grammar. The syntax of writing requires a single line of though, organised in a semi-chronological order from the start of the sentence to its end.
This is what we mean by 'logic' - the words (logos) put into a cogent order.
If we can write out an idea, we create its logic.
That does not mean its logic is sound, but it does mean it exists.
Thoughts without written or oral form are intrinsically underdeveloped as without clear communication, thoughts cannot be shared.
Although thoughts can be manifested without words:
Visual art, music, movement and the construction of any physical object are all thoughts manifested - but they are not as accurate to the original thought and more open to interpretation and misinterpretation that words.
Words are the closest analogue we have to thought.
As we order our words, the thought inspiring those words is reshaped. Something ephemeral is lost, but what remains gains greater solidity as ideas consolidate themselves around the structures of language.
As understood in the Sapir-Whorf Hypothesis , language shapes the way we think about the world.
Therefore, if we can improve our language and communication skills through things like writing using a Framework for thinking then we can improve (or at least influence) the structures of thought pre-vocalisation (oral and written). The mind adapts its thinking to better fit with the structures through which those thoughts will eventually be expressed.