Horst W.J. Rittel developed foundational theories and methodological frameworks on design science and planning theory. Rittel’s work is centered on the transition from traditional, engineering-based systems analysis to a more nuanced, social-negotiation-based systems approach.

The most critical takeaway is Rittel’s identification of "Wicked Problems"—complex social and planning issues that are inherently resistant to definitive formulation and traditional scientific solutions. Rittel argues that because these problems have no stopping rule and no right or wrong answers, the planning process must shift from an expert-driven model to an argumentative model. This model emphasizes the Symmetry of Ignorance, which suggests that knowledge is distributed among all stakeholders. Consequently, the role of the designer evolves from a technical expert to a midwife or facilitator who helps objectify subjective judgments through transparent, iterative discourse.

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1. The Nature of Planning Problems: Wicked vs. Tame

Rittel’s primary contribution is the distinction between two types of problems: Tame (German: gutartig) and Wicked (bösartig). While science and engineering were developed to solve tame problems, social and political planning deal almost exclusively with wicked ones. Tame problems can be exhaustively stated, providing all information needed for a solution (e.g., a mathematical equation or a chess problem). The solver knows exactly when the task is completed and the solution is reached. Solutions are objectively right or wrong, and they can be tested via trial and error without significant irreversible consequences. Wicked problems, on the other hand, defy the traditional scientific method due to the following traits. First, you can't understand the problem without having a solution in mind. The information needed to understand the problem depends on how you intend to solve it. Second, there is no internal logic that signals a "finished" state. One stops because of external factors like lack of time, money, or patience. Third, solutions are not objectively true; they are judged as "better," "worse," or "good enough" based on the values of stakeholders. Fourth, the consequences of a solution may unfold over an indefinite period, and unintended side effects may outweigh intended benefits. Fifth, every attempt to solve a wicked problem is significant and irreversible. There is no opportunity for "trial runs" or learning through harmless failure. Sixth, there is no exhaustive list of potential measures or operations that can be applied. Seventh, despite similarities, every wicked problem has distinct characteristics that prevent the direct transfer of past solutions. Eighth, every problem can be seen as a symptom of a higher-level issue. Ninth, the way a discrepancy is explained determines the nature of the solution. These explanations are often based on the "worldview" of the analyst. Finally, unlike scientists, planners are held liable for the real-world consequences of their failures.

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2. The Crisis of Systems Analysis: First vs. Second Generation

Rittel identifies a planning crisis stemming from the failure of First Generation systems analysis when applied to social systems.

First Generation: The Freight Train Model

This traditional approach follows a linear, phase-based sequence: Understand the problem - Gather information - Analyze - Synthesize solutions - Evaluate - Implement. It uses Operations Research to find the best solution within a defined solution space. Rittel argues this fails for wicked problems because you can't understand the problem as a separate first step; understanding and solving occur simultaneously.

The Paradoxes of Rationality

Rittel highlights four paradoxes that make traditional rationality (thinking before acting) impossible in its pure form. First, to be rational, one must investigate the consequences of an action. But investigating consequences is itself an action with consequences that must be investigated, leading to infinite regress. Second, there is no logical end to the search for further consequences. Third, the further into the future one projects consequences, the more uncertain they become, eventually making them useless for current decision-making. And fourth, a model must include the modeler and the model-building process itself to be truly comprehensive, which is logically impossible.

Second Generation: The Argumentative Approach

Rittel's Second Generation approach replaces the expert-dictated model with a social negotiation model. No one person has expert knowledge that trumps the local, lived experience of those affected by a plan. To avoid being planned for, stakeholders must be active participants in the process. The process must be objectified, meaning the grounds for subjective judgments are made explicit and communicable.

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3. The Argumentative Model of Planning

Rittel proposes that planning is essentially an argumentative process. Decisions are reached through the interplay of Issues (a question or problem that arises during planning), Positions (a potential answer or standpoint taken regarding an issue), and Arguments (Evidence or reasoning provided for or against a position).

Key Principles of the Argumentative Model

• Deontic Premises: All planning involves ought (deontic) statements (e.g., "we should build a bridge"). These can't be derived from facts alone but represent moral or political choices.
• Objectification: This is the process of making the basis of one's judgment clear to others. While objective in science means person-independent, objectification in planning means successful communication of subjective values so they can be debated.
• The Planner as Facilitator: The planner is not a doctor prescribing a cure, but a midwife helping to bring issues to light or a teacher guiding the discourse.

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4. Methodology: Variety and Evaluation

Rittel describes the design process as an iterative cycle of generating variety (creating options) and reducing variety (narrowing down to a choice).

Variety Generation (Expanding the Solution Space)

• Morphological Box (Zwicky Method): Planners identify key design variables and all their possible values. Combining one value from each variable produces a vast array of potential solution types (e.g., 17,280 combinations for a university expansion project).
• Systematic Doubt: Involves describing a situation in atomic sentences, negating them through doubt, and interpreting the negation as a new solution type.

Variety Reduction (The Evaluation Filter)

Reduction is achieved by applying Constraints (Zwänge) and Performance Models:

• Types of Constraints: Logical, physical, technical, economic, cultural, and political. Rittel notes that every constraint is a sign of resignation, an admission that certain factors will not be changed.
• Performance Metrics: The goodness of a building or plan is a function of performance variables (pk), design variables (dj), and context variables (ci).

Measurement and Subjectivity

Rittel emphasizes that goodness (quality) does not exist in the object itself. It is an Evaluation performed by a specific evaluator, for a specific purpose, at a specific time.

He distinguishes simple (nominal) classification (e.g., building types), ranking (ordinal; e.g., good, medium, bad); interval measurement, with constant units but arbitrary zero point (e.g., Celsius); and ratio measurement with a natural zero point (e.g., Kelvin, length).

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5. Summary of the Planners' Mindset

Rittel concludes that Scientific Planning is a myth. Planning is always political because it is based on deontic premises. The systematic methods of the Second Generation don't replace intuition; rather, they demand more spontaneous judgments at a finer level of detail. The goal of planning is not to find a singular truth, but to engage in a conspiratorial effort to share risks and manage the inherent wicked nature of reality.