5 ideas
Experiments such as Asch's line-judging studies and Milgram's obedience studies show that most people will deny their own perceptions to agree with a group, or harm others on an authority's instruction. Lessing argues this knowledge is available but not applied: it should be taught to children directly, so they learn to recognise these pressures in themselves as they happen and are less likely to be captured by them.
Imagine how later generations will judge us, the way we now judge witch-burners or crowds at public executions. Seen from that distance, our own mass emotions stop looking normal: war fever, the pleasure many people take in the excitement of war, and slogan-driven hatreds. The exercise works because it removes the feeling that 'everyone thinks this' proves something is right.
Lessing describes her own years as a committed Communist, beginning in 1940s Southern Rhodesia. She watched herself and her comrades adopt Party jargon, treat dissenters as enemies, and split into bitterly feuding factions, while holding convictions that later proved false. She presents this as firsthand evidence that intelligent, well-meaning people give their judgment over to a group without noticing they have done it.
A mind shaped by group certainty tends to swing to the opposite belief rather than leave the pattern behind. Lessing's example is former zealous Communists who became equally zealous anti-Communists, with the same rhetoric, the same need for heretics and the same absolute tone. What persists is the structure of belonging and certainty, not the particular doctrine.
Novels and histories let readers see human behaviour from a detached distance and notice patterns they cannot see while inside a group. Lessing treats this capacity for self-examination, and the open societies that allow it, as the individual's main defence against mass feeling. The person who can stand apart from the group's emotion is the one who can still think.