Thinking in terms of building physical buildings.. architects are often the visionaries but engineers are the realists. You know, architects come up with these crazy incredible building designs based on their engineering understanding, but ultimately it has to be vetted, proven and implemented by engineers.
I have, however, always wondered why people should be seen as "only architects" and "only engineers". While the separation of duties is critical to ensure the overall construction is sound, people can be visionary engineers, and people can be knowledgeable in both how to do something in real terms as well as dreaming on how to go beyond.
