Liang and Greenhalgh use the same two 1978 facts for opposite causal conclusions; only Liang explicitly joins them into one syllogism

chinapopulation-policyone-child-policyhistoriographycontested-causationcold-war-sciencegreenhalghliang-zhongtangsong-jianbridge-seed

Liang Zhongtang's 2009 essay and Susan Greenhalgh's 2003 article each hold both the June-1978 leading-group meeting and Song Jian's 1978 European encounter with population cybernetics (see observation-liang-2009-and-greenhalgh-2003-are-symmetric-shared-landlord), but the two historians put the pair to opposite argumentative use.

Liang concedes Song's foreign-derived method in §三 (pp. 68-69) and then explicitly joins the two facts into one causal argument in his concluding section §五 (p. 71), writing — "從時間上講，「一胎化」政策的產生與宋健的「科學預測」沒有 甚麼聯繫。「一胎化」政策最早可以追溯到1978年6月。當1980年2月宋健等人浮出水面 時，「一胎化」生育政策如同離弦的箭、出膛的子彈，早已實行了" ("Temporally speaking, the one-child policy's emergence has no real connection to Song Jian's 'scientific forecasting.' The 'one-child' policy can be traced back at the earliest to June 1978. By the time Song Jian and others surfaced in February 1980, the 'one-child' birth policy, like an arrow already loosed from the bow or a bullet already fired from the barrel, had long since been put into practice.") The meeting date is the premise that neutralizes the cybernetics-exposure fact's causal weight.

Greenhalgh does the reverse. Her June-1978 passage sits in a section ("The policy impact of the control theorists," pp. 185-186) that concedes "top leaders and population policymakers were moving toward adoption of a policy encouraging one-child families" from mid-1978 (already recorded) — yet still concludes "without doubt it was the Song group's work... that injected a sense of urgency into the policymaking process and changed minds," narrowing rather than abandoning the causal-credit thesis her 2005 China Quarterly companion piece states in stronger form. She never juxtaposes the June-1978 meeting against Song's 1978 Europe trip the way Liang does; the two facts stay in separate sections doing separate work.