Merrill delineates instruction into three specific programs or practices. A principle is defined as something that exists given the right circumstances and environment regardless of programming or practice; a practice is a specific activity and program is defined as a set of practices that is more or les prescriptive to fulfill the principles that are in play. (Merrill, 2002). This give rise then to the idea that instruction must be based on a asset of principles and establishing those principles are what are important and not merely attempting to propose a particular program that may or may not be suitable for every environment or learning scenario. Merrill goes on to discuss how he has found that regardless of model, there are still key principles that are being established for the instruction to be effective. His work captured not only the rigorous aspect of implementation but also of design from a much les esoteric level than merely prescribing a one size fits all models for every situation.

As a trained musician, this is a very easy concept to understand. In music there is a set of principles that applies to any situation given the right set of circumstances. When one goes on location one can very quickly look at his music and then begin to make connections and decisions based on what will be needed. These principles help to define what will follow. So then there is a real need, as Merrill points out, for there to be a content first modeling that allows for the instructional designer to see what the content is and then analyze the situation to determine what principles are important (Merrill, 2006). These set of first principles are common to the majority of all instructional scenarios, but the way that they are designed around and implemented could be quite different depending on the customized needs of the learning environment and learners themselves.

References
Merrill, D. M. interviewed by Silber. (Speaker/Author). (2006). Interview with D. M. Merrill [Online audio]. Minneapolis, Minnesota: Capella University.
Merrill, M. D. (2002). First principles of instruction. Educational Technology, Research and Development, 50(3).