Consider the enthusiasm demonstrated on the first day of school (any first day of school regardless of age). There is a mixture of excitement and hope. In the individual child there lies a burning question, "What will I learn today?" Buried under the social layers of seeing old friends and making new ones, children truly want to learn. "The real motivation to learn," says David Merrill, "comes when students are able to do something they were not able to do before."
I say, then, instructional design is the process of sustaining positive learning memories directly related to the learner being able to do something they were not able to do before. I conjecture the accumulation of such memories will support learner growth and development as well as encourage them to want to learn for a long time.
As for the disposition of instructional design, I say it is the combination of the art of teaching and the science of design with measures of common sense, compassion and care. Why? Simple, the perfect lesson plan does not guarantee success as does not an overdose of sensible love. There must be an orchestration of events, interactions, and results which move the learner along. Instructional design is this orchestration.