Taggart is the president of Taggart Transcontinental, Dagny's older brother, and the novel's most prominent villain. He is far worse than a corrupt businessman seeking wealth by parasitical means. Like his soulmate Lillian Rearden, Taggart is riddled with hatred for the good. His goal in life, which dominates his actions even when he doesn't recognize it explicitly, is to disfigure and destroy the men of the mind. He is a nihilist, one who seeks destruction of the good, and this characteristic dominates all aspects of his life.
Nihilism explains why Taggart hates Francisco, Dagny, Rearden, and Wyatt. It explains why he wants to hear Galt scream. It's also his primary motive for cannibalizing the Phoenix-Durango Railroad and destroying Dan Conway. To wound Hank Rearden is Taggart's sole reason for having sex with Lillian. To destroy the innocent hero-worship of Cherryl Brooks is his sole reason for marrying her. Taggart wants to celebrate the announcement of Argentina's transformation into a "People's State" not because of his anticipated profit, but because of the nationalization of d'Anconia Copper and the resulting financial destruction of Francisco d'Anconia.
Because man cannot live with the conscious realization that his purpose in life is destruction, Taggart is forced to evade understanding his true motives. He lies to himself endlessly, trying to convince himself that he seeks to gain wealth, to protect the interests of his railroad, to help "friends" such as Orren Boyle, or to serve the "public welfare." The truth is that Taggart doesn't value wealth, life, the railroad, success, Boyle, or the public. If "value" means to have a strong positive commitment to some life-enhancing person, object, or process, Taggart values nothing. On the contrary, he hates people capable of achieving values and living successfully. He is riddled with envy, which Ayn Rand defines as "hatred of the good for being the good." Only one thing compels him: to wreak such devastation that the good have no chance to survive. This is why, during a meeting that leads to the passage of Directive 10-289 (the laws designed to enslave productive men), Taggart involuntarily screams, "If we are to perish, let's make sure that we all perish together. Let's make sure that we leave them no chance to survive!"
Taggart's wanton destruction of Cherryl leaves him shaken because it brings his true motivation too near to the surface; the fabric of lies designed to protect him from the truth is in danger of crumbling under the strain. When he has Galt — the ultimate example of man's capacity to live and the symbol of all that he hates — in his power, his kill-lust peaks. He doesn't merely want to hear Galt scream; he wants Galt to die. When that realization bursts through into his explicit awareness, the motivation for his entire existence stands naked before him. No man can withstand the recognition of his own utter moral depravity. Taggart has evaded this recognition his entire life, and realizing this dreaded knowledge causes him to lose his mind.
Taggart endorses the doctrines of altruism and collectivism because they enable him to attack and enslave the productive men that he hates. He recognizes that the consistent application of these theories leads inevitably to national socialism and communism, which are totalitarian dictatorships that imprison and exterminate the independent minds that he loathes. The acts of mass destruction wreaked by such collectivist murderers as Adolf Hitler, Joseph Stalin, Mao Tse-tung, and Pol Pot are chilling real-life examples of the same nihilism that drives the actions of James Taggart. In Taggart's character, Ayn Rand lays bare the underlying premises of mankind's most evil representatives.