Growth is typically an indicator of success. It?is not always an end in itself ¨C in the case of waistlines, for example, it is side-effect rather than goal ¨C but it is usually a sign that things are going well.

So does this rule that bigger means better translate to higher education?

In marketised systems, such as the UK, growth has taken on much the same role as in business: rising student numbers are a marker of success and route to financial stability, while improvement in research output (both quality and quantity) is a standard measure of performance and reputation.

The number and size of universities is increasing in planned systems too ¨C?between 2000 and 2014, the number of students globally more than doubled to 207 million.

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There are good reasons for this expansion. Emerging middle classes see study as the route further up the ladder, and governments see universities as the engines of knowledge economies.

And yet universities are not driven by the same single-track dynamics as business, in which growth is a raison d¡¯¨ºtre, so there can be ambivalence about endless expansion.

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It is safe to assume general approval and appreciation of the need for higher skills, and for knowledge that advances human understanding, health and prosperity. But there is often something else too: a sense, regularly expressed in the UK, that more might mean worse.

In our opinion pages this week, Lord Willetts reflects on his achievement, as universities minister, in removing the cap on student numbers against the grain of austerity-era belt-tightening.?He remains convinced that it is vital for ¡°as many as possible who can benefit from it [to] have the opportunity of well-resourced higher education¡±.

He is right, and it is?important that this belief is preserved in the face of significant backlash from what Willetts calls the ¡°new school of edu-sceptics¡±.

There is also a debate about how size affects a university ¨C its relative strengths in teaching and research, certainly, but also its character as an employer and alma mater.

Might it be the case that a huge institution results in silos, for example, and makes isolation more likely? Could the mental health crisis in universities be exacerbated by size and its impact on individual well-being, a sense of supportive collegiality and belonging? Or is critical mass so essential to the academic process, and collegiality such a strong tradition, that these risks can be mitigated even in the largest of institutions?

In our cover story, we unpick some of these threads, and find a multitude of models and perspectives.

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For a world-leading research powerhouse with a major endowment to draw on, being small and exclusive may be a model that helps to maintain a relentless focus on excellence.

As the president of the California Institute of Technology (2,240 students, 349 academics, 30 Nobel laureates) puts it, ¡°we try to get better, not bigger¡±.

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There is also evidence that small teaching groups ¨C as at Oxbridge, or the elite liberal arts colleges in the US ¨C are beneficial for students, and that some staff find smaller institutions ¡°less corporate, more like a community¡±, as one academic at York St John University says.

But there are advantages too for large institutions, particularly in research ¨C?as is clear from?the upper echelons of the world rankings.

There are, perhaps, ways in which the devolved structure of universities can make even the largest universities more human in scale.

It is often said that academics feel more affinity to their discipline than their institution ¨C which may translate to a strong bond to their department, for example. The collegiate system operated by some universities is another approach.

For individual institutions, then, there may well be an optimum size for a given strategy and mission.

But, for systems, the more interesting question is about what a healthy ecosystem looks like ¨C and how to avoid policies or market mechanisms that encourage, or even demand, homogeneity.

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In higher education, there¡¯s no such thing as one size fits all.

john.gill@timeshighereducation.com