A Design System layout of components

Principles are fun-da-mental

Laying the foundation with ethos, pathos, & logos

Establishing the design principles for your Design System or product will provide structure. By identifying the core design principles of your product your team will use the same language.

Design principles are the qualities that make your product unique. They are the essence, and you can find this at the very core of your product. They communicate what the purpose of your product is all about. What is its voice, its personality? Can you identify the essence? These are questions to ask your team to find a common understanding.

Design Principles will serve you as a guide. They will become a cornerstone to building something meaningful with your team. Thus setting the design system in the right direction.

Elaborating on your principles

When building a product, you will need to explore the principles that will apply to it. Principles will be the guide of your product to those building it. Principles have the goal of having a shared philosophy. They bridge the gap between the various disciplines. These include your product (done internally to define what good design means to your product and team), company (these are the most common, found within the style guides), platform (for services or apps), and a universal set (including foundation and process). Design principles are not something that can be measured nor quantified.

Within the principles of your product, explain the purpose and shared values. What is the goal? Why do you have this goal? What are the values of the product and/or brand? Knowing the answer to these questions will help your team understand the objectives. Try asking your colleagues or within your company what the principles of your product are. Having shared values will help your team be consistent in what they are building.

These are some practical examples of design principles from AirBnB, Pinterest, & Paypal:

AirBnB’s design principles

Each piece is part of a greater whole and should contribute positively to the system at scale. There should be no isolated features or outliers.

Airbnb is used around the world by a wide global community. Our products and visual language should be welcoming and accessible.


We’re focused when it comes to both design and functionality. Our work should speak boldly and clearly to this focus

Our use of motion breathes life into our products and allows us to communicate with users in easily understood ways.

Pinterest’s design principles

It’s intuitive, not learned. It makes the user feel powerful. It makes the content taste better.

It’s colorful. It’s visually responsive. It’s unexpected

It’s built for exploration. It’s impossible to miss-tap. It’s reversible.

Paypal’s design principles

We Craft
We obsess over every pixel. Every word. Every experience. We make big changes in tiny spaces and small tweaks to global ideas. We won’t release anything we’re not proud of. Because focusing on the details lets us build something truly memorable.

We Simplify
Building something simple is anything but. So, we’re honest about our impact on people’s lives. We respect their time and spend every waking moment of our day making things simpler. Because simple is loved, needed, used, and shared.

We Connect
We create opportunities by connecting people. That’s a powerful concept–coming up with ways to connect and further interconnect our world any way we can. It’s an awesome challenge, too. One we dive into headfirst every day.

We Go All In
We invent, then reinvent. Design, then redesign. Yes, we butt heads sometimes, but only because we’re fighting for the people that depend on us. Our customers need us to do the best work of our lives so that they can do the best work of theirs.

When writing your design principles, they should be written practically. When written simply, the principles become vague. Designer Alla Kholmatova explains that “a principle should offer practical guidance on how to solve a design problem within the context of a specific product”.

Can you design and build better products with a set of standards in mind? Keep in mind that getting the definition may also take a few iterations.

Ethos, Pathos, Logos applied to Design

The use of Ethos, Pathos, and Logos comes from Aristotle. These three elements form the Rhetorical Triangle. Aristotle’s Rhetorical Triangle provides strategies for a writer to appeal to the audience. Aristotle taught that a speaker’s ability to persuade an audience is based on how well the speaker appeals to that audience in those three different areas.

I learned to use ethos, pathos, and logos as techniques of persuasion within advertising. If this aspect interests you, StudioBinder’s post provides more insight on the topic. This is how they’ve summarized the terms: Ethos calls upon the ethics, or what we’d call the values, of the speaker. Pathos elicits emotions in the audience. Finally, Logos puts logic into play by using evidence and facts.

This post isn’t about writing, speaking, or selling. It is about design and its principles. How could Aristotle’s Rhetoric apply to a Design System, Brand, or Product? Is the rhetoric applied within them or to them? The word principle is used instead of the word virtue. This is because we are talking about rationale as opposed to faith.

Let’s start with Ethos. Ethos appeals to ethics, character, and morals. Is your product trustworthy? What you are designing establishes credibility. Within Aristotle’s argument, to be trustworthy, 3 things needed to be present :

The actual definition is the goodness of a person. Aretē identifies with what enables a person to live well or successfully. What allows your own product / or system to be successful? What best practice would you apply to your process?

It means practical wisdom or practical intellect. This term includes judgment, understanding, and insight. Yet it must result in the appropriate action. Practical wisdom can be applied to a system or product through collaboration. Furthermore, your product and/or design system will constantly change. This is due to the continued learning about its interaction with the world in a long-term feedback loop. It is not about knowing, but your capacity to acting on it and structuring it.

It means “good-will” or “beautiful thinking”. Aristotle applied this term to the notion of friendship. He observed that friendship is “wanting what is good for the sake of another” because a friendship is reciprocal. The term implies a condition of receptivity. How will your product be perceived by others?

Pathos appeals to emotions. This will rely on the content and the strategy of your product, rather than design. How will your product connect with the users?

Finally, Logos. This is the logical appeal and reasoning. When building your Product or Design System, you apply logos by using facts (ie. quantitative research, statistics, expert input, or informed opinions). Part of logos within a product or system is the accessibility to information.

Designer Dan Mall writes a “design manifesto” at the start of every project. It contains the creative direction, a point of view, what you are going to do, and what you are not going to do. Well-written design principles provide qualities that are open to interpretation. Yet grounded to the specific product.

As a takeaway, the design principles should provide a perspective and be memorable. If they are forgettable, you may want to give it another try. I hope this read has provided you with new insight.

Thanks for reading! ✌🏼

Hi! This is Flo. I am a UI/UX Designer, specializing in Design Systems, Interface Design, and Art Direction. I am based in Berlin, Germany. www.florodriguez.com

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