Why was thomas paine common sense considered radical

Because it  played a crucial role in convincing colonists to take up arms against England.

Explanation:

Hi, "Common Sense"  written by Thomas Paine,  is credited as playing a crucial role in convincing colonists to take up arms against England. In it, Paine argues that representational government is superior to a monarchy or other forms of government based on aristocracy and heredity.

Paine proposed ideas to the colonists, three ideas for a change.

1) Declare Independence  

2) Create a Republican state government

3) Union of the new states

.Its simplicity but accuracy helped the colonist understand it more easily.

first representative government in british america called virginia assembly