Lego logics

There’s been a lot on reddit lately about Lego bricks: How many Legos, stacked one on top of the other, would it take to destroy the bottom brick? There’s lots to learn from toy construction sets, not least how creativity happens … or doesn’t.

Giant red, yellow and blue Lego blocks ... bigger than a carIn the first flush of enthusiasm for artificial intelligence and automated knowledge-based systems back in the 1980s, some of us thought that at their most creative, people employ two kinds of intelligence. There’s (i) the generative and (ii) the interpreting kind of intelligence.

We thought that generative intelligence in architecture requires rules about how components go together. Interpretive rules are those from which you derive some kind of meaning, or a description of the way the building will perform. The trick is to use both kinds of rules (knowledge) to produce designs that are functional and meaningful. In a book on Knowledge-Based Design Systems published in 1990, we explained the two kinds knowledge in terms of Lego bricks:

Consider a child’s construction set (such as a set of Lego parts). Inside the box is a vocabulary of plastic parts which fit together according to a syntax of composition, determined by the plug and socket connections between parts. The designs that result can be interpreted as spaceships, moon buggies, cars and houses. The interpretation works both ways. If the child wants to play with a “truck,” he or she appears to translate this “meaning” into a particular set of design charactersitics — four wheels, a platform, and a cab. Using knowledge of the vocabulary and syntax, he or she constructs a design with those characteristics (p.58).

Box lid showing children playing with a toy house

Meccano box: open with contents visibleWe also thought there was some practical advantage with this division, particularly if you want to create computer programmes that designers would use, or that could even automate some aspects of the design process: produce office floor plan layouts, or design stairs to fit in small spaces.

If design is a rule-based activity, then you might have different rules for each kind of knowledge: rules for generating and rules for interpreting. An automated “design system” would need both generative and interpretive knowledge.

It sounds plausible, but there are major problems with Lego logics. Here are just a few.

  • There’s a lot of research into the automated production of designs using knowledge as rules, constraints, algorithms, networks, and schemas. As anyone working in the area knows, the process is bedevilled by the so-called “combinatorial problem.” There are many millions of ways of organising even a handful of Lego blocks. (See interesting online article: “A Lego counting problem.”) Testing them all beats the capabilities of any computer, and clever short cuts are never generalisable to all design conditions.
  • To think of human intelligence, capability or aptitude in terms of rules or algorithms is very limiting. Knowledge is tacit rather than explicit. It’s not as easy to identify design rules in real-world design situations as it is to fit Lego bricks together. The goal of any design task is ill-defined in any case.
  • The idea of knowledge bases makes it difficult to accommodate the social, political, cultural and contextual, ie the contingent. Put simply, it leaves out the people.
  • Design approaches that focus on generative knowledge put a lot of emphasis on making forms and shapes, as if designing is just a matter of manipulating Lego bricks. Critics attribute some of the least human, even if starkly beautiful, environments to a configurational approach to building cities, eg Oscar Niemeyer’s National Congress complex in Brasilia.
  • The dual-knowledge idea (generative v interpretive) perhaps reinforces the idea that there are two cultures, or even two kinds of people. There are those who are good at designing buildings (the creatives), and there are those highly adept at criticising, reviewing, evaluating, and writing about buildings (the interpreters). This division between the creators and the critics has a long history.
  • Some colleagues and I think it’s more useful to now think of making and interpreting as part of the same process. In Interpretation in Architecture, Adrian Snodgrass and I argued that to design is to interpret. See What does it all mean?

As it happens, whatever you say about making can be applied to interpreting and vice versa. So there aren’t really two types of knowledge. Perhaps there are thousands … or just one.


  • Coyne, Richard, Michael Rosenman, Anthony Radford, M Balachandran, and John Gero. 1990. Knowledge-Based Design Systems. Reading, Mass.: Addison-Wesley.
  • Mitchell, William J. 1990. The Logic of Architecture: Design, Computation, and Cognition. Cambridge, MA: MIT Press.
  • Stiny, George. 1980. Kindergarten grammars: designing with Froebel’s building gifts. Environment and Planning B: Planning and Design, (7)409-462.
  • Vale, Brenda, and Robert Vale. 2011. Lott’s Bricks, The Arts and Crafts movement and Arnold Mitchell. Architectural Research Quarterly, (15) 2, 119-130.


  • Also see De-generation, Neuroscience eclipses AI, Wicked problems revisited, and Brain scans and creativity.
  • In Knowledge-Based Design Systems we thought of spaces of designs and spaces of interpretations. The design task is to derive designs that satisfy the constraints implied by both kinds of knowledge. To reason “backwards” from functions/meanings to define a space of designs required reasoning about constraints, or a kind of reasoning known as evidential reasoning, or abduction. I now think this model and its variants are outdated and limited. However, such quasi Venn diagrams can take on a surreal cast, which is appealing. See for example Graham Shawcross’ blog post on Visual Thinking.

Venn diagrams with connectors


  1. Do you know that Lego used to produce a set of bricks for architects called modulex which were just 20x10x5mm and came in a tasteful range of architectural colours; beige, grey and transparent and that some of schools of architecture had large sets for making physical models with.

    Lego now has a sub-brand called Lego Architecture that has kits of parts for making iconic buildings, Falling Waters, Sydney Opera House etc.

    Gabby also sent me a link to a free universal construction kit that allows you to print bricks that can join up different construction kits Lego, StickleBricks etc.

    It is a bit frustrating not being able to put images in here, so I will create a separate post with more stuff in it particularly about Bayko and design grammars.

  2. That’s helpful to know about. I went to Legoland in Denmark (next to Billund airport) expecting to see a showcase of Lego products, history, including robotic components, etc. It really is just an amusement park, unless I missed something. I wonder if there’s a Lego museum somewhere.

    1. The V+A’s Bethnal Green Museum of Childhood is probably the place.

      “Our collection includes famous examples of building kits from many of the leading makers including Richter Anchor Blocks, Meccano, Lotts, Minibrix, Bayko, Kiddicraft, K’Nex and Lego. … ”

Leave a Reply