The Law of Raspberry Jam is one of gerald-weinberg's consulting heuristics from secrets-of-consulting-1985: "The wider you spread it, the thinner it gets." In its original context the law concerns consulting influence — a consultant who tries to change everything in an organization ends up changing nothing, because their attention and energy are spread too thin to produce real traction anywhere.
The Heuristic
The image is deliberately homely. Raspberry jam spreads. When you spread it over more surface area, you get less jam per unit area. This is not a profound mathematical insight; it is a reminder of an obvious constraint that consultants and managers routinely forget.
Weinberg's application: a consultant who identifies twenty things that need to change in a client organization, and tries to address all twenty simultaneously, will make less progress than a consultant who picks two or three and goes deep. Influence requires concentration. Diffused attention produces diffused results.
Extended Applications
Weinberg extended the law beyond consulting influence to several other domains:
Management attention. A manager responsible for too many people, projects, or problems cannot attend to any of them adequately. The Law of Raspberry Jam is an argument for span-of-control limits, not as bureaucratic formalism, but as a cognitive and organizational reality. See also general-systems-thinking's treatment of variety and control: a manager whose attention is spread too thin has insufficient variety to respond effectively to each situation.
Organizational communication. Organizations that try to communicate everything to everyone end up communicating nothing clearly. The corollary is that decisions about what not to communicate — what to leave out — are as important as decisions about what to include.
Feature development. A software product that tries to do everything does nothing well. This connects the law to broader arguments about focus, coherence, and the costs of scope expansion.
Relationship to Consulting Practice
The Law of Raspberry Jam is one of several heuristics in secrets-of-consulting-1985 that address the structural conditions of consulting influence. Weinberg's helpful-model-of-consulting holds that a consultant's goal is to help the client become more capable, not to deliver a large volume of recommendations. The raspberry jam law operationalizes this: focus your influence so that it actually takes hold, rather than broadcasting recommendations that the organization cannot absorb.
This also connects to rudy-block-rule — the paradox that people resist change whether comfortable or uncomfortable. If a consultant spreads their intervention too thin, they trigger resistance everywhere without building sufficient momentum anywhere to overcome it.
As a Systems Thinking Observation
From the perspective of general-systems-thinking, the Law of Raspberry Jam describes a resource allocation constraint in a system with limited control variety. Weinberg consistently used memorable aphorisms like this to name dynamics that systems thinkers would describe in formal language — feedback saturation, attention bandwidth limits, control variety constraints. The informal name makes the concept portable and memorable in ways that formal descriptions are not.