diff --git a/src/controller.js b/src/controller.js
index <HASH>..<HASH> 100644
--- a/src/controller.js
+++ b/src/controller.js
@@ -9,7 +9,7 @@ var util = require("substance-util");
 // Application Controller abstraction suggesting strict MVC
 
 var Controller = function(options) {
-  // this.state = null;
+  this.state = {};
   this.context = null;
 };
 
@@ -30,6 +30,15 @@ Controller.Prototype = function() {
     this.state = state;
     this.trigger('state-changed', this.context, oldContext, state);
   };
+
+  // Inrementally updates the controller state
+  // -----------------
+  //
+
+  this.modifyState = function(state) {
+    _.extend(this.state, state);
+    this.trigger('state-changed', this.state.context)
+  };
 };
Implemented modifyState method.