I bet it would be super easy for a smart guy like you to state simply and directly just why this is so.
And then please tell us all how much manufacturing is sufficient to constitute this "base".
OK, I’ll play. Not smart, I just live in a country that is a few years further down the path yours is following.
It is pretty simple.
If you make nothing, what do you have to trade? And if you make nothing, trade you must with those who do produce the things you want and need.
Ideas? That ain’t worked out so well in terms of employment, has it. R&D has an upfront cost that has to be met by someone. Remember the joke when Windows 95 came out? The most dominant operating system in the world sold one copy to China.
Services? To who do you sell them? I live in the banking capital of the world and, according to my son in law who works in the City, you could replace 90% of the people there with a computer and have no downside.
Raw Materials? Ask the Canadians how well that works. The extra value is in the working of the raw materials from high bulk, low profit goods into low bulk high profit goods.
Making actual physical things to sell domestically and for export kicks the whole economy into high gear. Not just at whatever plant is producing the things for sale. You need drivers, which means you need truck builders, road crews, heavy plant builders, shipwrights, steelworks, marine engine makers, powerplant and line workers .... You get the idea.
When we lost a Honda plant here, the official layoff was 1500 people. In fact, it was nigh on 5 times that, thanks to associated layoffs. The reverse holds true too. When a plant is built, employment skyrockets.
As to how much would constitute a base, say 40% of domestic consumption. Roughly what Norway and Germany have and it seems to have cushioned them from the worst effects of the recesion. High enough to be competative, high enough to ensure employment for them as want to work (and some who don’t) and high enough to support R&D without bailouts or grants.