What is the logic of design proposals? What argument is or needs to be made when you present a design? What is it that a design proposal does and what criteria must it meet to perform this function?
Engineering can be contrasted with science in that it is not only descriptive, but also prescriptive. The goal of a scientific paper is to describe and explain the world as it is. An engineer’s design prescribes or at least proposes what should be done or changed in the world: ‘if you have a certain goal, then here is a plan to achieve it’.
This makes a design proposal, in rhetorical terms, an argument about policy. Much of it may be concerned with facts and causation, in the end it is a question of means, ends, and value. Such an argument is always relative. The proposal can be compared to existing options, alternative proposals, and to leaving the situation unchanged. And while scientific claims aim at universality, designs are always context-dependent, appropriate to a specific time and place.
If this is the argument we need to make, how do we argue it?
A design report usually combines a design proposal with a description of the process that led to it. But the providence of a plan does not necessarily provide a justification for it, just as the events that led to the discovery of some scientific fact or theory play no role in the decision to accept it as true. It is simply impossible for the psychological origins of a design idea to have any effect on how it will perform in the real world.
In practice, however, we do find a design proposal more convincing when there is a design process to ‘back it up’. And when we present a design, it is customary to include a description of the events and activities that led to it. What’s going on here? Is there a difference between design development and scientific research that means that the process of discovery is relevant to the logic of justification in the first while it is not in the latter? Do design and engineering vindicate the logical positivists? Or do the steps in a systematic design process somehow serve a dual function of stimulating discovery while also providing the raw material for building the subsequent case for justification?
When we ask ‘Where did this idea come from?’, I don’t think we are asking for a justification of it by means of the logical chain of reasoning that led to it. What we’re actually, and justly, interested in is ‘What exploratory experiment was this a response to?’, ‘What other options is this an alternative for?’, ‘What is this idea meant to achieve, exactly?’, ‘How come you expect this feature to lead to the effects you predict?’, and so on. These questions address the logic of justification, but their answers are generated in the mess of sketches, models, diagrams, and other thoughts that are generated in the process of discovery. So it is not the process itself that serves as justification, but the products of that process do serve as building blocks for an argument in support of its outcome.