Among all of the lessons that have been learned by the financial services industry in the past couple of years, one that apparently still hasn’t sunk in is that you can’t have it both ways. For a business built on trust and confidence, it’s a stance that’s untenable and, ultimately, self-defeating.

Just ask Goldman Sachs, which now finds itself in the tricky position of defending itself from allegations that it structured a long product for one client with input from another client who planned to short it, and that the firm stood quietly in the middle. It remains to be seen whether the U.S. Securities and Exchange Commission can prove any legal wrongdoing. But there’s no question that playing such an obviously conflicted role can undermine a reputation for honesty and integrity.

This sort of attitude isn’t limited to Wall Street. For example, at the height of the recent financial crisis, the Canadian banks welcomed globally co-ordinated policy action when that meant aggressive interest rate cuts, the provision of extraordinary liquidity and mechanisms to buy up their troubled mortgage securities. They insisted they needed a level playing field with global banks receiving similar support. Yet, with that same level playing field now leading to higher capital requirements, tougher liquidity standards and possibly new taxes to weigh against the sector’s excesses, suddenly Canadian bankers are aghast at the notion of adopting these reforms.

Nor is this stance just a product of the latest financial crisis. The instinct to try to have it both ways seemingly runs deep in our industry. On the regulatory front, the securities industry has long insisted that disclosure is sufficient investor protection, and that regulators need not entertain the notion of restricting commission arrangements or imposing a fiduciary duty on advisors. Yet, it resists any effort to improve that disclosure.

The current pension reform debate reveals the same sort of doublethink. Firms warn clients they must save for retirement because the public pension system is hopelessly inadequate. But when the government proposes reforming the system, the industry tells policy-makers that it’s actually working just fine.

For a business that purports to dispense wisdom and encourages a long-term view, the financial services industry often behaves in a short-sighted way. It should realize that you can only play both sides for so long before you fracture trust for good.