We lack methodological principles for how to draw contemporary insights from historical texts. As a result, many efforts to do so have failed – more than most people realise. One key principle is to get historical authors right, by reading them accurately, and by improving their ideas if needs be. This can help us challenge false claims to historical authority, debunk parochial contemporary explanations, ask new questions, or suggest new answers. The second main principle is to get contemporary authors and issues right. This is where scholars err most. Some scholars fail to demonstrate a gap in the literature, over-generalise, misread contemporary authors, underestimate the complexity of contemporary issues, or use outmoded ideas: just as history of political thought can liberate us, so too it can constrain us. Overall, I suggest, some of the boldest claims for the contemporary value of history of political thought come from scholars whose own contemporary insights are not as convincing as they think. Far from highlighting the contemporary relevance of history of political thought, this risks making it look irrelevant. A less disdainful approach to contemporary political theory and philosophy is vital.