In class we discussed the question of whether the thought, or the idea came first. This is obviously very similar to the chicken and the egg debate, but I would argue that the idea came first. From a young age our thoughts categorize objects, and identify concepts that we are taught to associate words with at a later age. Simple ideas, as we defined in class, are those ideas that need no interpretation for us because we have experience with it in the natural world. Locke said that "Any words will serve for the recurring of our own thoughts to serve our memories, a man may use whatever words he pleases to signify his own ideas to himself and there will be no imperfection to them, if he constantly uses the same sign for the same idea he cannot fail to have his meaning understood"(817). Assuming that words are a constituent of language, and language is a means of communicating and understanding, I believe that ideas were communicated and understood without words in primitive societies, as well as in our infancy.
Locke argues that the connection between a word and the idea it signifies is not natural, when an infant sees a bottle their mind does not perceive it as "milk" or any sound distinction. The bottle is the infant's understanding of a means to satisfy hunger, and the infant will communicate their desire for the bottle without the use of words until they come to associate the sounds of words like "milk" and "bottle" with the means to satisfy their hunger. Another example was given in class about rubbing two sticks together to make a fire. This entire process could be communicated without the use of language, or words. Locke says that we develop simple ideas from sensations, the warmth of that fire, or fulfillment of craving, and that the words that we use to signify these ideas are purely conventional.
I'm sure that Locke would find these simple examples to be a part of the natural human capacity to hold some truths, but a concrete theory cant have an undisclosed number of instances in which it doesnt apply. If everyone's ideas are derived from experience, and everyones experiences are different, then any given word will signify an idea that is different in every person. Therefore, I think Locke has certainly made a case for the failure of language. The birth of the idea prior to the creation of the word seems to be proven several times in Locke's treatment of the word as a "signifier" for an idea. However the paradox will always exist that someone has the idea but needs signs to express it.