Somewhere in your organisation there is a plan that is working. The team executes, the numbers arrive, the reviews are calm. And it may already be failing, in the one way a review cannot see: the world that made the plan correct has moved, and the plan has not noticed.
Peter Drucker spent his last decades consulting for organisations in exactly this state, and in 1994 he gave the pattern a name. Every organisation, he argued, runs on a theory of its business: a small set of assumptions about its environment, its mission, and what it is genuinely good at. Strategy, hiring, pricing, the org chart — all of it is downstream of those assumptions. The organisations that stumble are rarely lazy or stupid. They are disciplined executors of a theory that has quietly stopped being true.
The word theory is doing real work there. A theory is not a vision or a value; it is a set of claims about reality that can be wrong. And claims about reality expire. The customer who made you does not stay the customer. The competence that won the last decade becomes a commodity. The environment that rewarded your structure rewards a different one now.
Write the assumptions down, then date them
His method begins embarrassingly simply: state what the organisation must currently believe for its behaviour to make sense. Not what the strategy document says — what the behaviour implies. If your team spends most of its effort defending an existing product line, it believes that line is where the future revenue lives. If your hiring is all senior specialists, you believe the problems ahead look like the problems behind.
Then put a date on each belief. When was this last tested against something outside the building — a result, a customer decision, a lost deal? An assumption that has not met reality in three years is not knowledge. It is a habit with a budget. Drucker's sign that this had happened was behavioural too: an organisation working harder and harder at what used to work, results thinning while effort climbs. Running faster on expired assumptions feels, from inside, exactly like discipline.
The test he recommended is behavioural, not rhetorical. Noncustomers are the sharpest instrument: the people who should buy from you and do not. Growth in your market that you are not getting is the environment telling you which assumption has expired, and it does so years before your own numbers do — your own numbers are generated by the customers your theory still fits.
Watch out for
The failure mode of this method is turning it into an annual ritual. An offsite that re-affirms the existing assumptions in fresher language has performed the ceremony and skipped the point. The signal that it is working is discomfort: a session that ends with every assumption intact should be treated as a failed test, because in a moving environment at least one belief is always past its date.
It is also fair to say what the method cannot do. Naming an expired assumption does not tell you what the new one should be. Drucker was better at diagnosis than at the redesign that follows, and the essay itself says more about noticing decay than about building the replacement. The redesign is a harder, longer piece of work, and pretending the diagnosis is the cure is its own expired assumption.
Answer this next
What is one thing your current plan requires to be true that nobody has checked against the world since the plan was written?
You do not need a workshop for that. You need the plan, a pencil, and an honest half hour.
