Sustainability and resilience face an implementation crisis. To address this I propose a vocabulary of paradox where the price of clarity is either paradoxical theory or thoughtless action. Praxis, understood as reflective practice and practical reflection, occurs in the ‘muddled middle’ as researchers and practitioners resolve experience into generalised paradox and dissolve it into specific action. In the vocabulary of paradox this is the paradox of praxis: knowledge gives action meaning and action gives knowledge meaning. Applying the vocabulary to sustainability and resilience, I propose that both can be understood as articulations of a paradoxical desire for both continuity and change in human social-ecological circumstances. I define sustainability as the continuity of valued attributes of human circumstances both by means of and in the midst of change. Sustainability is continuity through change. This definition emphasises values (what should continue and change), understanding (what does continue and change) and human agency (what can be influenced to continue and change). All three merge in the muddled middle of implementation and are paradoxical in theory; continuity requires change and change requires continuity. Implementation of sustainability and resilience initiatives necessarily invokes a first person perspective. Here I propose a third paradox, the paradox of people, whereby people both constrain and enable each other. I argue that paradoxical agency for sustainability and resilience can be articulated in terms of these three paradoxes of praxis, people and sustainability: knowing and doing, together and apart for continuity and change. Finally, I propose the role of a sustainability agent, understood as both a change agent and a continuity agent, to support the paradoxical agency of individuals and small groups as they implement sustainability and resilience initiatives. I argue that this approach to sustainability and resilience dissolves the implementation gap and provides a practical and empowering vocabulary to make sense of sustainability praxis. I support these arguments with examples drawn from experiential research and interviews with conservation and sustainability practitioners in the North East region of the small Caribbean island of Tobago, West Indies.