This chapter suggests some ideas to integrate biological with psychological theory. It discusses defence and safety with a more detailed investigation into their function. The defence signal detection system is built upon simple reflexes and sensory-motor patterns. The activation of the defence system releases primitive response routines. The activation of the safety system, when following defensive activation, reduces defence system arousal and can release innately available response routines. The output and psychomotor components of the safety system differ from those of the defence system. The chapter also argues that the psychomotor system of defence is organised around go-stop, whereas the outputs of the safety system do not have a stop component but are regulated by increments or decrements in arousal acting through the positive reinforcement system. The evolution of significant others being capable of activating safety systems and de-activating defence systems links immediately with the importance of secure attachment and social support.