Having no perfect substitute is probably the easiest way for the econ 101 student to attack the orthodox. My econ 101 prof insisted that oil shale was an example of a substitute for conventional oil, without any discussion as to costs. Unfortunately, no one at the time had the knowledge or courage to retort, "then why do people in power say we are dependent on Middle East oil?"

Price ought to, and on occasion has, reflected scarcity: During the '70s oil shocks and recent price behavior. Another problem is that perfect competition mostly exists in textbooks, along with perfect information, which is requisite for both perfect competition and perfect markets.  

Expectation theory also affects price as the so-called war premium shows so well: If Israel had met with success [from its POV] in Lebanon, would oil be under $60 now and the DOW over 12,000?

Lastly, externalities are NOT accurately included in price for any commodity--indeed, almost all products. For example, oil and gas extraction south of New Orleans is responsible for much of Katrina's devastation, yet that future foreseeable cost was NOT factored into the price of the resources extracted; nor does it appear that the massive environmental costs of bitumin mining is included in the pricing of its extraction; nor was the cost of climate chaos included in our past or current fossil fuel pricing.

I think that's enough information for the 18-year-old econ 101 student to argue against econ 101 orthodoxy regarding "infinite" "finite" resources. All that is needed is the courage to confront the "knowledge authority," not an easy task, one much easier for us "non-traditional" students.