Nonperturbative method in field theory: The gauge technique

We present a derivation of the gauge-technique ansatz, which emphasizes the approximations made in regard to the truncation of the Dyson-Schwinger equations. The nonperturbative nature of the method is elucidated. Finally we extend the technique to nongauge settings. This is possible because for fermionic theories which are not necessarily gauge theories Ward identities exist in the infrared limit. To illustrate these features a simple model is solved in the infrared region