This leads to the following equation
$$ \nabla_{\boldsymbol{\Theta}}\log{p(\boldsymbol{X};\boldsymbol{\Theta})}=\nabla_{\boldsymbol{\Theta}}\left(\sum_{x_i\in \boldsymbol{X}}\log{f(x_i;\boldsymbol{\Theta})}\right)-\nabla_{\boldsymbol{\Theta}}\log{Z(\boldsymbol{\Theta})}=0. $$The first term is called the positive phase and we assume that we have a model for the function \( f \) from which we can sample values. Below we will develop an explicit model for this. The second term is called the negative phase and is the one which leads to more difficulties.