THE medieval alchemists who tried to transmute base metals into gold shrouded their theories in impenetrable mystic language. By comparison Jean-Claude Juncker, the president of the European Commission, was restrained in his choice of metaphor as he announced his long-awaited investment package this week in the European Parliament. His plan, he said, was a "watering can" that would nurture the European economy back to growth. But he appears to have placed his hopes in the same mysterious forces channelled by the ancients in their gnostic quest. With a hint of reproach to his predecessors, Mr Juncker argues that the EU is facing its "last chance." Populists and demagogues, he suggests darkly, lie in wait if Europe cannot find the will to tackle its problems of low growth and high unemployment. Sceptics doubt whether Mr Juncker, a longtime prime minister of Luxembourg and consummate Brussels insider, is the man to reinvigorate Europe. But even before taking office on November 1st he signalled that he meant business, streamlining the clunky structure of the commission and promising a clutch of early initiatives. Chief among these was a planned three-year €300 billion ($374 billion) investment fund. Europe has woefully underspent on infrastructure in recent years. Public investment in the euro zone last year was 2% of GDP, half the American figure. Mr Juncker is particularly interested in sprucing up European transport, digital and energy grids. Even so, for some months the details of his package, especially where the money would come from, remained elusive. All was revealed on November 26th, when Mr Juncker unveiled his plan in Strasbourg. His new European Fund for Strategic Investment (EFSI) will, he says, mobilise total spending worth €315 billion, even more than his initial number. A task force of independent experts will produce a list of potential projects, covering not only conventional infrastructure projects but also education and R&D. Red tape will be slashed and rules harmonised to improve the investment climate. Thanks to this, said Mr Juncker, "we are offering hope to millions of Europeans disillusioned after years of stagnation." Yet look more closely into Mr Juncker's golden package and the contents seem rather leaden. Just €21 billion of the €315 billion is public money, none of it genuinely new: €16 billion of it will come from existing EU funds, the rest from the European Investment Bank. This seed money is meant to allow the EIB, which will house the EFSI, to lend some €63 billion. And, in a final act of transmutation, this funding will unlock €315 billion of capital in all: institutional investors, reckons Mr Juncker, are itching to deploy their money if only the conditions are right. The EFSI will provide "risk protection" to the EIB, letting it invest in trickier, more complicated projects without jeopardising its AAA rating. Assuming the EFSI grinds its way through the EU's bureaucratic machinery, it will spring into life next summer. It will run for three years; should it prove successful it may be given another three. If Mr Juncker does manage to spin gold from his €21 billion, the plan is expected to create 1m-1.3m new jobs. That would be welcome, but Europe's jobless stack is 25m people high, and officials acknowledge that more is needed. This is where Mr Juncker's second alchemical act comes in. He hopes the political momentum his plan builds will serve as a philosopher's stone in Europe's capitals, encouraging national governments to chip in to the EFSI's capital, or to co-finance projects directly. As an incentive the commission will exclude such contributions from its calculations of budget deficits. France and Italy, in other words, may not spend more to stimulate their own economies but can fork out for Europe's. Such are the peculiarities of a Europe seemingly awash with liquidity but bereft of trust. We're caught in a (investment) trap Mr Juncker's diagnosis of Europe's ailments is mostly fair enough. And he is working within tight constraints: public debt across the EU stands at 87% of GDP, and German hostility to more spending makes a New Deal public-works programme impossible. But for the same reasons he risks over-promising. Proposals similar to his have foundered in the past, at European and national levels. Before the money starts to flow, projects must be designed, investors secured, planning permission obtained and so on. And even if Europe is flooded by a torrent of private cash that the commission insists is available, there are no guarantees that governments will fill Mr Juncker's coffers. Having hyped a package that may amount to no more than 0.8% of EU output over its three years, he will be left exposed if the results are frustratingly small - even if he can blame others. Early responses from most analysts have been muted, at best. This presents a political danger. Mr Juncker's presidency got off to a rocky start when, just four days after he took office, newspapers published lurid details of supposedly sweetheart tax deals secured by hundreds of multinationals in Luxembourg on his watch. In response a ragtag of fringe MEPs have called a vote of no-confidence in Mr Juncker, although it was due to fail as The Economist went to press. Indeed, in a final feat of alchemy he is trying to transform this row into a debate over tax harmonisation in Europe, something he has long urged. If his investment package flops the disappointment will not be easily dispelled. Mr Juncker is not well known to voters and was not elected by them; he may be personally insulated from their wrath. But he can ill afford to alienate national leaders, on whose good graces he depends to succeed at his job. Europe's recent experience demonstrates how quickly economic discontent can turn into Eurosceptic fury. That is one act of transmutation that would not be to Mr Juncker's advantage.