Kevin is right. There is a subtlety here, and if you're not quasi-anal about how you let knowledge to get into your head, you might miss it.
When I first learned semiconductor physics, I remember being almost offended at one professor's proclamation that the base current "controls" the collector current. This simply isn't true. First, the base current is smaller than the collector current, and second, if you remove the application of potential from collector to emitter, you can still get current flow, but the original model breaks down. What then?
Is there a relationship between IB and IC?? Yes, of course. But the purist/fundamentalist quickly sees there the base current doesn't really "control" anything, and the charge distribution model is for more appropriate. Here, the differnce in potential causes a certain distrubution of chage in a 3-D space on all sides of the P-N junctions, and there is drift, diffusion, and recombination of this charge leading to current flow based upon the application of Gauss/Poissons/Maxwell/Einstein/Fick's Laws, and it is this special arrangement from which the flow of current is determined.
So the second intepretation is intuitive and permits much greater insight than the other, and allows the engineer to remain useful when someone starts taking the model and twisting it around, as did one astute professor who understood the mechanics so well that he would take circuits and rearrange the transistors in ways few people would dare try, then still managed to predict with suprising accuracy the behavior of the circuit without help from a computer. My guess is that he was relying on the voltage-control (charge distribution) model, not a neatly packaged concept of Bf.
-Chaud Lapin-