It is difficult to debate what Helen Keller perceived to be reality. In her own narrative, she equates knowledge with happiness because it enables her to be understood. Her voice is validated with knowledge and in being able to communicate with others, happiness is evident:
My work was practice, practice, practice. Discouragement and weariness cast me down frequently; but the next moment the thought that I should soon be at home and show my loved ones what I had accomplished spurred me on, and I eagerly looked forward to their pleasure in my achievement.
I can see her point here in that the authentication and validation of voice is where individuals can find happiness. Considering that she lived the earliest points of her life in total silence from others, with a voice that was not understood, it makes sense that she would consider knowledge and happiness would go together. There might be another element here, though. The idea of power could come in being able to be understood. Helen finds happiness in being able to gain more knowledge. Yet, there is happiness in being validated and power comes from this. Part of her own being is that she gains power from gaining knowledge and the ability to express it. This construction of power might not be "all world encompassing," but it enables her to be understood more clearly. In this, there is greater knowledge evident, and through this, more power over her own being is also evident.