In an ideal world there would be no defence industry, nor defence spending. In the world we have, however, these are essential and so the challenge is to make this expenditure as useful as possible.
This week's International Defence Exhibition (Idex) and the related naval show Navdex remind us that sound military spending entails more than just buying maximum "bang for the buck".
Ever since the first steel sword was forged, military needs have been a prime driver of technological progress. Even the internet, ubiquitous in daily life, has its roots in a US defence agency.
It follows that leveraging defence expenditure to advance the country's high-tech know-how, and its engineering and manufacturing skills, is a self-evidently sound policy. And as we are seeing at Idex, that policy is being pursued vigorously by the UAE - and by others.
But the first role of defence industries is still defence. A strong military posture is essential to the UAE, which has resources others might covet, in a region not exactly conflict-free. For a country this size the appropriate policy is sometimes called the "poison shrimp" doctrine, as once articulated by Singapore: we may be small but we would prove indigestible for any would-be aggressor.
This means the UAE needs not only its alliances but also national armed forces that are well-trained and equipped, for military needs as well as for relief work in any natural disaster. This in turn means we need a domestic military industry. And while some aircraft and other big-ticket items will continue to be bought from abroad, there is sound logic in the move towards joint ventures with foreign firms, deals that can start to move UAE companies into these fields - military-plane maintenance, for example.
The UAE's defence industry is fully aware that in weapons systems, as in other manufactured products, foreign sales permit longer production runs, cutting unit costs. Meanwhile, it also makes sense for allied nations to benefit from "interoperability" of gear and best practices. And when local defence firms don't tailor their products to the needs of the local armed forces, the industrial side of the equation gets short-changed.
For these reasons the flurry of announcements at Idex is welcome. A pact with Italy to step up naval technology cooperation; plans by defence group Tawazun to buy a controlling stake of Al Jaber Land Systems; Mubadala's joint venture in military-aircraft support with Sikorsky and Lockheed Martin and other such accords will all provide jobs, increase skills and add capability across our economy.