[The] stock market, by its own action, continually indicates the probable
direction of its immediate and future trend, and anyone able to determine
this with accuracy should attain success in trading and investing.
Coming events [are] foreshadowed on the tape because large interests
there disclose their anticipation of advances or declines by their
purchases or sales. So, too, with the large speculator who is endeavoring
to raise or depress prices. If one were to become sufficiently expert, he
could judge by the action of stocks what is in the minds of these large
interests and follow them.
The trend is simply the line of least resistance. When a stock meets
opposition in its rise, it must either be strong enough to overcome this
resistance (selling) or it must inevitably turn downward, and when, in its
downward course, sufficient buying is encountered to halt the decline,
it [must] turn upward. The critical moments in all these various phases
of the market are these minor and major turning points. (Wyckoff)