You speak in order to be understood. That is so ordinary that it can hide. You also talk in order to think: you try a sentence aloud, you write a clause to see whether you meant it, you keep a name in mind so that a thought will not slip. Language is doing two jobs at once, and both are already yours.
Timothy Kearns, in The Principles of Discourse, names those two jobs as the natural purposes of language.
Language has two purposes naturally: it is used for communication and as the principal instrument for aiding human thought.
The first is the one everyone grants. We live with others. We cannot do the work of a human life — raising children, making a living, keeping a peace, handing on a craft — without making our thought available to someone else. Kearns’s word for this is simple: we are social animals. Coordination requires communication. Human communication in language is not a private glow that happens to leak. It is thought expressed in a public way, so that others may understand what has been expressed.
Human communication in language is the expression of thought in a public way so that others may understand what has been expressed.
The second purpose is easier to miss. Thought is fleeting. It turns, it doubles back, it will not sit still to be examined. When we put a thought into words we can hear or see — spoken, written, remembered as a sentence — we give it a form we can return to. Then we can ask two questions that are almost impossible to ask of a thought that has no saying: did I say what I was thinking, and does this saying fit the thing I meant to think about?
Other aids do some of the same work: a diagram, a column of numbers, a sketch. Language is the aid always to hand, and the one that can be about anything we can consider. Definitions, which every serious inquiry needs, are linguistic. Results, when they are to be kept and taught, are stated. Even the student who wants to begin from data is already using this instrument whenever the data become a report.
The two purposes are not rivals. We refine thought by expressing it, often as if to another person, and then we offer the refined thought to others because we live with them. We also receive most of what we come to understand through words from parents, teachers, and those further along in a practice than we are. A community of learners is, in that sense, a community of speakers. For both reasons it has to care for names, statements, and speeches.
Continue to Discourse and the three arts.