How does one define a government being to the left or right of the political spectrum?
The first task is to define what the opposites of the plane are. Locke explains in his work Two Treatises of Government That man is free through the natural rights of life, liberty, and property. Locke than further explains that through the creation of all governments men conditionally transfer some of their rights to the government to ensure the protection of their natural rights. By using Locke’s baseline we can see that on one side of the coin is the absence of government and the only laws are the natural ones (not to be confused with divine laws). On the other side Locke would call governments that fail to meet the obligation of protection of the basic natural rights of life liberty and property. These governments attack natural rights and control the population. He goes into great depth in the Letters Concerning Toleration by explaining how the government should never use coercive power of the citizen to force an action the ruler believes in. Locke comes to this idea from the philosophers that came before him and together they.
Now that we have the baseline to all governments we can build the scale. For this we will use 100 to 1 where 100 is total rule by the government over its citizens. where the government no longer protects the natural rights, but destroys the ability for the citizen to retain their rights. 1 is the absence of government as a whole where the individual is tasked with protection of their natural rights. Since we now use the concept of left and right instead of a numerical scale we use the definitions of how left and right are viewed today. Conservatives, libertarians, tea party etc consider themselves right wing and the democrats and social progressives see themselves as left wing. As such in These United States the far right is 1 and the far left is 100 on the numerical scale. This is how the political scale is built upon and why all governments are to the left of no government it comes down to the control each government has over the citizen and their ability to freely exercise their natural rights.