Politicians are often criticised for sound-bite politics, catering to the needs of 24 hour media. In this environment the value of political rhetoric can easily be questioned. But talk isn’t cheap and sometimes scrutinising the actions of politicians based on what they’ve said can be even costlier. Ask any former Lib Dem supporter about the party’s tuition fee pledge prior to the 2010 General Election.

With large sections of the electorate only choosing to switch on late in the electoral cycle, party leaders will be hoping that a well crafted and delivered speech in the coming four months will deliver a host of additional support. This may be so, but sadly the art of good speech writing is anything but easy. So what makes a good political speech, and what should we be looking out for between now and May?

Arguably Ed Miliband’s most successful speech over the course of this Parliament was his 2012 party conference speech in which he announced Labour’s energy price freeze policy. Miliband seized the political agenda and rebutted claims up to that point that Labour lacked policy substance. This would seem to suggest a good speech needs a ‘meaty’ policy at its heart, in order to energise supporters and set the terms of the political debate.

The Greek philosopher Aristotle would disagree. He literally wrote the book on the topic, On Rhetoric, back in the fourth century BC. Aristotle is widely considered to have initiated the study of rhetorical theory and how politicians aim to persuade voters. He provides a more comprehensive set of analytical tools in which to judge political rhetoric.

Aristotle states a political speech aims to persuade a voter by one of three ways, these are via the ethos (character), pathos (emotion) and logos (logic). The ethos refers to the character of the speaker and the way in which the speaker seeks to use this to their advantage. Take for example David Cameron continuously reiterating in speeches about how the Conservatives have brought about the economic recovery. In his rousing 2014 party conference speech, Cameron utilised this rhetorical device to underline his own economic credentials, while discrediting Labour, “You cannot be prime minister of this country and forget the most important issue that we face”, referring to Miliband omitting any mention of the deficit in his own party conference speech. Was Cameron’s speech a success? The Tories enjoyed a small bounce in the polls while support for Labour continued to ebb away.

For pathos, or the emotion of the speech, take Miliband on the NHS as an example. By pledging additional NHS funding and labelling the situation in the health service as a crisis, Miliband is not only trying to stoke fear in voters about another five years of the NHS under a Conservative Government, he is also claiming Labour are the only party that can save the NHS. Finally, the logos, or logic, is often the most easily identifiable aspect of a political speech – “You can’t trust Labour on the economy because they crashed the car in the first place.” Simple.

Whichever politician it is giving the speech, they will not simply draw on just one means of persuasion, but utilise combinations of all three. Take the statement above about Labour on the economy. That isn’t just a logical argument that Labour have no economic competence because of the party’s past record, it is also seeking to discredit the party’s character. In Aristotelian terms, this is an etho-logical argument.

A truly good political speech is multi-dimensional. Miliband’s acclaimed speech in September 2012 on energy companies was not a good speech purely because of the policy announcement. Miliband drew heavily on the negative sentiment and emotion voters have towards energy companies and energy prices, which he followed with a logical solution – the energy market is broken so Labour will fix it. That said, one of the defining problems Miliband has faced as leader over the last five years is the fact people have doubted his ability as leader. In essence, his ethos has been called into question, which has made the art of persuasion more difficult as a result.

At this stage in the Parliamentary cycle, we know the arguments that each party will use, on the economy, the EU or immigration. Through the prism of Aristotelian rhetoric, we also know the means by which each party will seek to persuade voters. The only thing we don’t know is which of these will actually persuade the most voters on election day.