Regardless of our profession, most of us like to think we know what we’re talking about - especially during this Financial Inclusion Week. But how much do we know, really? Assumptions and heuristics (‘rules of thumb’) dominate more than most of us would readily admit. And why not? Usually they’re good enough. Before Galileo upended astronomy, existing models, regardless of how wrongheaded, were still good enough to maintain calendars, predict agricultural seasons, and support navigation. Since the beginnings of modern microfinance in the 1970s, we have likewise relied on similar orthodoxies: that take-up of microcredit was a demonstration of its inherent value to the clients; that on-time repayments were evidence that clients were not over-indebted; that competition would inevitably lead to lower interest rates. And, perhaps most importantly, that targeting specific groups of clients would inherently create social benefits: lending to the poor would alleviate their poverty, lending to women would strengthen their roles in society, lending to farmers would improve their yields, etc., etc.