1. What design principles actually are (and aren't)
A sample chapter from Design Principles in Practice, a field guide by Ben Brignell.
Design principles are often mistaken for best practices, heuristics, mission statements, or aspirational slogans. The difference matters. Without clarity about what a principle actually is, it becomes difficult to use one to guide real decisions.
Design principles are decision-making tools.
Design principles are not aspirations, values, or slogans. They help teams choose when the right answer isn’t obvious.
Principles exist to reduce debate, not eliminate thinking.
They don’t force agreement. Principles clarify what matters so decisions can be made.
Principles are often confused with laws and rules.
This confusion is one of the main reasons they fail in practice.
| LAW | RULE | PRINCIPLE |
|---|---|---|
| Must | Must | Should |
| Universal | Enforced | Contextual |
| Binary | Specific | Interpreted |
Laws are universal and non-negotiable.
Breaking them produces failure regardless of context, intent, or interpretation.
Rules define specific behaviours.
They are enforced, auditable, and useful when consistency matters more than judgment.
Principles guide decisions, not actions.
They don’t tell you what to build, but how to choose between options.
To understand the power of principles it helps to see how they are different to laws and rules. To see this distinction in practice, let’s imagine you want to transport a valuable antique vase.
You pack the vase in a box and write “DO NOT DROP” on it in big letters. The box may not be dropped but it could easily be crushed when a heavier box is placed or dropped on top of it.
You could write “DO NOT CRUSH” on the package. However, it may still be dropped, or transported upside down, damaging the vase in a different way.
So you could write “THIS WAY UP”. It may still be mishandled, dropped, crushed, left to slide around in the back of a van…
Each of these rules protects against a specific, known failure mode. You could write all three rules on the package but it would end up being too complex and would likely be ignored.
A single principle “FRAGILE” communicates intent. It relies on judgment rather than enforcement. It allows people to adapt behaviour to the situation in front of them. It empowers the delivery person to make appropriate choices about how they would handle your parcel.
Treating principles like laws makes them brittle.
When principles are enforced rather than interpreted, they stop guiding decisions and start policing behaviour.
Good principles trade flexibility for clarity.
They constrain choice in order to protect outcomes that matter.
Principles are system-bound.
They only make sense within the context of a product, team, or organisation.
If a principle cannot be bent or consciously broken, it is being misused.
At that point, it has become a rule, whether intended or not.
Principles do not replace judgment.
They focus it.
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