Key People
Mentors, rivals, and fellow travelers — the human network behind the most dramatic arc in activist investing.
Bill Ackman
Founder & CEO, Pershing Square Capital Management
The subject of this knowledge base
Carl Icahn
Nemesis & Rival Activist
Ackman's great antagonist — opponent in the Herbalife war and the defining rivalry of both men's public lives
Hunter Harrison
The Exemplar CEO
The railroad operator Ackman installed at Canadian Pacific — the living proof of the right-CEO thesis
J. Michael Pearson
The Cautionary CEO
The Valeant CEO Ackman backed, defended, and joined on the board — the wrong right CEO at the center of his largest loss
Warren Buffett
Intellectual Mentor (at a Distance)
The distant model for Ackman's fourth act — simple predictable businesses and permanent capital
Charlie Munger
Intellectual Influence
The source of the inversion discipline and the mental-models foundation beneath the Eight Commandments
Paul Hilal
Former Partner
Ackman's partner and the operational architect of the Canadian Pacific campaign
Benjamin Graham
Foundational Influence
The intellectual ancestor — the price-versus-value framework Ackman inherited through Columbia and adapted into activism