What does it mean that I can speak, or write, English? The Turing test suggests testing for sapience by having a computer dialogue with a tester and, if it can fool the tester into thinking it is a human (generally, the tester talks to many computers and humans, and has to guess which is which), then it ought to be considered sapient. The test was originally presented by Alan Turing in this article: http://www.loebner.net/Prizef/TuringArticle.html, one interesting reaction was that of John Searle, where he used his, now famous, Chinese Room argument against the Turing Test.
The Chinese Room argument goes something like this: suppose I am in a room, and you send a page through with various symbols on it, in the room, I have a set of instructions for writing other symbols on another page of paper, which I then send out of the room. As it turns out, the pages that get sent into the room and the pages I send out of the room form a conversation in Chinese that anyone who didn't know any better would think took place between two native speakers of Chinese. But I do not know one word of Chinese. Even if the rules were for spoken Chinese and I learned the rules so well that I could walk around and have conversations in Chinese, I still would not know what I was saying. Now, this appears to be all the computer needs to do in order to pass the Turing Test, and thus it would not necessarily understand what it was saying.
However, I would know how people converse in Chinese. I would not know that this was what I knew, but I would know it all. Once you tel me "that is a conversation in Chinese" then I can say "I understand how speakers of Chinese converse" despite the fact that I cannot say that I understand Chinese. What if, as I am walking around, talking Chinese, I go to a restaurant and the waiter says something to me, to which I reply as my instructions dictate. The waiter then says something else, to which I again respond, after some time, he leaves. I have no idea what just happened, though I think that I just ordered something. Later, the waiter brings me food. Now, all I know is that, through that string of interaction, I just ordered this food. Later, I enter a fast food place, and, again have a conversation. This one is much shorter, and I receive a hamburger at the end. As I go through this process many times, in many environments, I will eventually learn how to ask for various foods in particular, whether the instructions point them out or not. With the instructions, it seems, I cannot ask for a hamburger because I want a hamburger, but only because someone has asked me what I want to eat.
To understand, and to speak, a language, then, I must be able to use it to get certain responses according to my desires. Now, if this is how language works, it seems odd not to include body language in it, since I reach out my hand to shake someone else's as a greeting. Thus, there is a way in which anything we do in order to get certain responses is an attempt at speaking a sort of language. I would argue that there is, therefore, a sense in which all of our actions constitute a sort of language. In other words, for every action I do, I do that action because of something, which that act therefore displays. So, if I do action x, based on y, then action x is an, even if only partial, display of y, which is usually a sort of desire, which is to say, a value judgement: "I want this" is equivalent to "I value this." Language, as the term is usually used, is used to refer to spoken actions, such as when I make a statement or ask a question. Ethics may be considered the study of how to tell the truth about the nature of things in all actions. This is not to say that speech is no more important than action. Speech has a certain clarity which actions lack, and is thus better for articulating, especially nuances about, what is true.
That which is of utmost value is God, and thus the most valuable actions are those which display a form of godliness, since those display what our idea of the most valuable is. In all our acts, then, we either speak truths or lies about God. This is sin: to lie about God. God is love, therefore we ought to display his love. What, then, of those attributes of God which we ought not, and cannot, hold? God is omniscient, omnipotent, therefore we ought to love his knowledge, and love his power. We ought not seek knowledge for itself, but seek God's knowledge because it is of God, and God's power, in and through his Spirit, because it is God's. There is not, therefore, in the end, a distinction between God's communicable and incommunicable attributes. In all God's attributes we, in some way, partake of them in our union with Christ. Not fully, as of yet, but to the extent that we are united to Christ. Thus, we love in part, we know God in part, and we act with the power of God in part--we have the power to move mountains, because it is the very power which raised Christ from the dead which now enlivens us to love and good works, and it is by the knowledge of God imparted to us that we are thus united.