a third time rejects the bill or bills that were the subject of the double dissolution, the Governor-General may convene a joint sitting of the two houses to consider the bill or bills, including any amendments which have been previously proposed in either house, or any new amendments. If a bill is passed by an absolute majority of the total membership of the joint sitting, it is treated as though it had been passed separately by both houses, and is presented for royal assent. The only time this procedure was invoked was in the 1974 joint sitting. Trigger event The double dissolution provision comes into play if the Senate and House twice fail to agree on a piece of legislation (in section 57 called "a proposed law", and commonly referred to as a "trigger"). When one or more such triggers exist, the Governor-General may dissolve both the House and Senate – pursuant to section 57 of the Constitution – and issue writs for an election in which every seat in the Parliament is contested. The conditions stipulated by section 57 of the Constitution are: The trigger bill originated in the House of Representatives. Three months elapsed between the two rejections of the bill by the Senate ("rejection" in this context can extend to the Senate's failure to pass the bill, or to the Senate passing it with amendments to which the House of Representatives will not agree). The second rejection occurred in the same session as the first, or the subsequent session, but no later. There is no similar provision for resolving deadlocks with respect to bills that have originated in the Senate and are blocked in the House of Representatives. Though the Constitution refers to possible actions by the Governor-General, it had long been presumed that convention required the Governor-General to act only on the advice of the Prime Minister and the Cabinet. However, as the 1975 constitutional crisis demonstrated, the Governor-General is not compelled to follow the Prime Minister's advice. In these cases, he or she must be personally satisfied that the conditions specified in the Constitution apply, and is entitled to seek additional information or advice before coming to a decision. Practice and misconceptions As a High Court Chief Justice Barwick observed in a unanimous decision in Cormack v Cope (Joint Sittings Case) (1974) (with emphasis added): History There have been seven double dissolutions: in 1914, 1951,