Feature Christmas 2012: Research

Building a metaphor: Another brick in the wall?

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e8302 (Published 17 December 2012) Cite this as: BMJ 2012;345:e8302
  1. Douglas G Altman, director
  1. 1Centre for Statistics in Medicine, University of Oxford, Wolfson College Annexe, Oxford OX2 6UD, UK
  1. Correspondence to: D G Altman doug.altman{at}csm.ox.ac.uk
  • Accepted 15 November 2012

The metaphor of studies being bricks from which a wall is being built leads to new ideas about accumulating knowledge, explains Doug Altman

A common metaphor for the accumulation of scientific knowledge is of individual studies being the bricks from which a wall is being built. Each study contributes to the growing structure as “another brick in the wall,” a phrase that appears in hundreds of journal article titles on PubMed. Inspired by the clear similarity of the ideas in Forscher’s wonderful allegory1 and a witty comment of Poincaré,2 I acquired many related citations by multiple searches with Google and Google Scholar over five years (see box).

Brick and building metaphors

  • “Of metaphors applied to science, the most evocative is the building of an edifice of knowledge with every paper serving as a brick”3

  • “The individual primary paper is not the final form of the consensus but it is the brick from which the whole edifice is to be built.”4

  • “Research scientists are trained to produce specialised bricks of knowledge, but not to look at the whole building.”5

  • “We speak piously of taking measurements and making small studies that will ‘add another brick to the temple of science.’ Most such bricks just lie around the brickyard.”6

  • “Science is built up of facts, as a house is built of bricks; but an accumulation of facts is no more a science than a heap of bricks is a house.”2

  • “Authors view acceptance of a manuscript as the completion of a piece of work—but for the research content of the paper, it is only the beginning. To contribute to the research enterprise, other investigators need to take the findings and build on them. But the construction of science requires solid bricks, not cardboard.”7

  • “And then it came to pass that a misunderstanding spread among the brickmakers . . . The brickmakers became obsessed with the making of bricks. When reminded that the ultimate goal was edifices, not bricks, they replied that, if enough bricks were available, the builders would be able to select what was necessary and still continue to construct edifices.”1

  • “It became difficult to find the proper bricks for a task because one had to hunt among so many. It became difficult to find a suitable plot for construction of an edifice because the ground was covered with loose bricks. It became difficult to complete a useful edifice because, as soon as the foundations were discernible, they were buried under an avalanche of random bricks. And, saddest of all, sometimes no effort was made even to maintain the distinction between a pile of bricks and a true edifice.”1

  • “After these bricks were used so well and were no longer fresh, however, they often ended up on shelves gathering dust or stacked in dark corners of offices and libraries. Indeed, many quite elegant ones went to such places directly, perhaps being too hot to handle, delivered too late to be useful, or too heavy for the users to bear. After some years the landscape was covered with bricks of many different sorts and sizes. A few brick makers began to ask if something interesting and useful could not be built with all these bricks. Some argued that what could be built with them might be as useful and important as the individual bricks themselves. Several went so far as to suggest that new bricks be crafted in such a way that they would be more useful for building something after they were used for their more immediate purposes. Needless to say, other brick makers thought these notions were a foolish waste of time and were not even what the craft of brick making was all about. Nonetheless, a few eccentric brick makers put aside their brick-making tools and began to collect used bricks and assemble them into different configurations to see what they might build from them. They soon learned to make interesting and useful constructions by stacking and arranging the thousands of bricks their colleagues had fashioned. And thus was born a new craft among the brick makers, the craft of building edifices from bricks or, as some liked to call it, Meta-brick making.”8

  • “The moment we are introduced to science we are told it is a cooperative, cumulative enterprise. Like the artisans who construct a building from blueprints, bricks, and mortar, scientists contribute to a common edifice, called knowledge. Theorists provide our blueprints and researchers collect the data that are our bricks . . . To extend the analogy further yet, we might say that research synthesists are the bricklayers and hodcarriers of the science guild. It is their job to stack the bricks according to plan and apply the mortar that makes the whole thing stick.”9

  • “To . . . utilize Forscher’s brickyard analogy, research synthesis as a primary research endeavour can both assemble random bricks into useful edifices of knowledge, and ensure that any bricks that are produced in the future contribute to the construction of such edifices rather than being thrown onto a random pile.”10

These quotations from over a century emphasise that scientific knowledge is cumulative, but also that completed research studies—the “bricks” of knowledge—have to be put together meaningfully; otherwise, we do indeed just have a pile of bricks.

Bringing together, in a systematic review or meta-analysis, multiple separate studies dealing with a particular question is a more focused variant of the same idea, dealt with in several of the quotations. And systematic reviews incorporate explicitly the notion of searching for the relevant evidence, among the countless thousands of publications.1


The primary message here is that scientific progress is made in small incremental steps, by many individuals and groups over many years. It is a continuous process. Thus, the accumulation of knowledge is not like completing a giant jigsaw puzzle, with explicit boundaries, but more like building a brick wall extending without limits. This rather simplistic image fails to indicate the likelihood of many holes in the wall, perhaps large ones.

These ideas about accumulating knowledge lead to two others, which have become more familiar. Firstly, research findings should be presented in such a way that they can be incorporated into future meta-analyses. Secondly, the bringing together of existing knowledge can inform the conduct of future research. Indeed, it should do so:

“If, as is sometimes supposed, science consisted in nothing but the laborious accumulation of facts, it would soon come to a standstill, crushed, as it were, under its own weight . . . The work which deserves, but I am afraid does not always receive, the most credit is that in which discovery and explanation go hand in hand, in which not only are new facts presented, but their relation to old ones is pointed out.”11


Cite this as: BMJ 2012;345:e8302


  • I thank Iain Chalmers for helpful discussions.

  • The author has completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declares: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Not commissioned; externally peer reviewed.