No members of the city council will vote in favor of the proposal. If one member of the city council ought to vote against the proposal, the other members should abstain in the vote on the proposal. The proposal should not be decided by the city's voters. If not every member of the city council abstains in the vote on the proposal, the matter will not be decided by the city's voters.
Activist: Any member of the city council ought either to vote against the proposal or to abstain. But if all the members abstain, the matter will be decided by the city' s voters. So at least one member of the city council should vote against the proposal.
The conclusion of the activist's argument follows logically if which one of the following is assumed?