Without pr there is no mandate (for a party) to rule

First past the post enables a single party to gain overall control of the government. This means that the entire country is owned and controlled by one party and one leader. This is a form of slavery... even though we can choose a different leader (of the opposing party) at the next election. Whilst we can say that any form of government is equivalent to slavery... clearly pr is not so offensive as compared with fptp. With pr it is generally impossible for the country to be controlled by a single party and if they are it is because that party has been chosen above all others. With fptp the governing party does not have a similar mandate because often they get elected on less than half of the vote and even otherwise people are compelled to vote tactically. Single-party rule has a mandate only if it is elected proportionally... they do not have a mandate if they are elected via fptp because people have not been given a free choice. No (non-coalition) government has a mandate if it is not elected proportionally. And since coalitions are not governments then governments only have a mandate under pr... but (since coalitions are not government) it is very unlikely that a government with a mandate will ever exist because pr elections tend to result in coalitions and not an absolute majority for a single party. A government with a mandate can only exist if a single party gets an overall majority under pr... which is very unlikely to happen. No (single party) government has a mandate unless pr is used. Government mandates require pr.