You can run slicks that are much larger like 2 inch Big Apples by Schwalbe and as long as you keep the pressure up the fatter tyres will roll just as well as the thinner ones.
Larger tyres will take the pressure.
Actually a large balloon tyre, such as Schwalbe's Big Apple, is designed to be run at low pressure to provide pneumatic shock absorption. For example their 26x2.0 is
designed to go as low as 2 bar (30 psi), and the 26x2.35 as low as 1.5 bar (22 psi).
As mcshroom said, it is the skinny slicks that are designed to hold and run at high pressure. A good example is
Conti's Sport Contact 26x1.3, it is nearly half the weight of the Big Apple despite having decent puncture resistance, and is designed to run at 80 psi.
Tyre selection should be horses for courses. For rough uneven terrains large tyres at low pressure will provide not only superior comfort but actually lower rolling resistance since the large volume of air at low pressure enables bike and rider to glide over the undulation without converting it into vertical motion and horizontal resistance while maintaining good traction. This is why many mtb riders go tubeless (via UST, Stans, ghetto etc.), not really for weight reduction, but to enable tyre pressure to go really low without having to worry about pinch flats.
This
scientific assessment provides some interesting instructive results and explanations.
For smooth fast roads, as we all know the opposite is true - light, skinny high pressure slicks provide the lowest rolling inertia and rolling resistance. One should however try to ensure the tyre is suitably wider than the rim as suggested by Sheldon at the bottom of this
page. Some mtb rims, such as Mavic's EX729, are too wide for narrow slicks.
If one runs a large tyre such as the Schwalbe Big Apple at high pressure, one is getting the worst of both worlds, i.e. poor pneumatic suspension while spinning an unnecessary mass of rubber. If one runs skinny tyres at low pressure, then one would be susceptible to pinch flats and even rim damage.
