Dialogue
Interaction Design concerns itself with the dialogue between a person and a creation. This dialogue is usually found in the world of behavior; the way someone may hold their knife and fork while cutting into a steak, or the gaze of another on a beautiful chair, following the twist of the wood as it twines around and through. Nature seems to understand dialogue, as the give and take of plants and animals in harmony creates the beauty and wonder of the world in which we live. The conversation stretches across species and over long stretches of land, and what is left is the beauty of our natural world.
Dialogue is complicated, and the designer can hardly compete with evolution. To design behavior - to create, and control the will of another - is next to impossible, and the interaction designer finds themselves simply understanding behavior and retrofitting their designs to match. While this certainly aids in comprehension and can create usable creations, it certainly doesn't ensure designs with staying power; this sort of stay is thought of as timeless, or priceless, or simply desirable.
The artist makes a statement, a distinct argument, through their canvas or clay or metal, and the audience responds; a conversation evolves, through acceptance, or rejection, or understanding, or bewilderment. The artist has no responsibility to the audience; clarity of message is irrelevant as long as understanding of emotion is communicated. I do not understand your message, yet I understand that I do not like it; the audience is able to form opinions and actions without truly becoming intimate with the content.
The designer has a harder task. Their work is of language, and words, and meaning; they must create a design language that assists the viewer not only in experiencing the emotion but also in truly understanding the content. This understanding goes deeper than usability, as the understanding is not of function nor of goal. The comprehension must be of intent; the audience must actually realize the intentions of the designer, and embrace the culture of the language that is spoken. This is not a metaphor; the designer does not "design as language is spoken". In fact, design is language, and the linguistic quality of form and topic are spoken through form and object. The poet selects a topic and paints a vivid understanding of scene through character, time, and the beauty of the language; the product designer selects an object and forms a vivid understanding of context through shape, weight, color, and material.
The interaction designer, however, speaks both words and form at once. They structure a compelling argument and invite the audience to share in their work; the work evolves over time, and the work is completed by the presence and synthesis of the audience. User centered design, as practiced, does not give credence to the true importance of the user: the creation lays dormant until the user truly and honestly understands the beauty of what has been stated.