The Prohibitory Act was legislation passed by the British Parliament in December 1775. It cut off all trade between the colonies and England, and removed the colonies from the "King's Protection." In doing so, in over six months before the Declaration of Independence, George III and Parliament had disbanded their relations with the colonies and proclaimed England to be at war with its former colonies. Many Americans believed that the king had given them no choice but to declare independence.
In October, 1775, George III in an address to Parliament had made it plain that he would be satisfied with nothing less than the complete submission of the colonists. Two months later Parliament passed the law known as the Prohibitory Act, which, supplementing the Restraining Act, prohibited all nations from trading with the American colonies and provided that all ships engaged in colonial trade were to be forfeited with their cargoes and become lawful prizes of war.
The law, being a virtual declaration of war, furnished the colonists with an excuse for throwing off all allegiance to the king. John Adams regarded this act as the straw that broke the camel's back.
The action of Parliament now indicated that the crisis had been reached and that the American people must choose between submitting to the tyrannical course of the mother country, or persisting in their resistance to aggression and wrong. They must now either retrace their steps with shame and dishonor or prepare to push forward and sustain their position at the risk of their lives. Though there was great uncertainty of ultimate success, the colonists faltered not. They chose the latter course and resolutely prepared to make the best possible resistance. Furthermore, bitterness was added by the employment of foreign mercenaries to fight the battles for the English, and this measure precluded the possibility of reconciliation with the mother country. It convinced the rebellious colonists that nothing less than a long and costly war would gain for them the freedom they so much desired.
In Parliament, statesmen like Charles Fox(who opposed the act) recognized the folly of treating the colonists as they were being treated, and in the American colonies, patriot leaders realized that the king was not to be reasoned with.
In order to reduce the Americans to submit, you pass laws against them tyrannical and cruel in the extreme. When they complain of one law, your answer is to pass another more rigorous than the former. You tell us that you have no choice in the matter, because they are in rebellion. Then treat them as rebels are wont to be treated. Send out your fleets and armies and subdue them, but show them that your laws are mild, just and equitable, and that they are in the wrong and deserve the punishment they meet with. The very contrary of this has been your wretched policy. I have ever understood it, as a first principle, that in rebellion you punish the individuals but spare the country.
In a war against a foreign enemy you spare individuals, and do your utmost to injure and impoverish the country. Your conduct has in all respects been the reverse of this. When the Boston Port Bill was under debate, I advised you to arrest and punish the offending persons. But you preferred to lay under a terrible interdict the whole population of Boston, innocent and guilty alike. And now, by the bill before us, you not only do your utmost to ruin those innocent men who are unfortunately mixed up with the guilty on the mainland of North America, but you starve whole islands of unoffending people who are separated from the rebellion by loyalty and unconnected with it by their political action and their political sympathies. - Charles Fox
John Adams noted of the act that "It throws thirteen colonies out of the royal protection and makes us independent in spite of our supplications and entreaties."
For a more detailed treatment, see Common Sense.
While these disheartening measures were being passed by Parliament, something to offset them had occurred in America. This was the publication by Thomas Paine of a pamphlet entitled Common Sense. Though an Englishman, Paine had early imbibed the spirit of Republicanism, and having an intense hatred of oppression, the style and manner of his pamphlet were such that they instantly aroused the energies of the colonists and fired their passions to maintain the struggle for liberty. In this pamphlet, Paine used every available argument on the subject of independence and employed every means of reaching all classes of people.
To impress the religious element, he employed the Scriptures and the name of the king was rendered odious in the eyes of those colonists who had read the history of the Jews as recorded in the Old Testament. He used the history of the children of Israel to show the foolishness of revolting against a government instituted by Heaven itself, and clearly portrayed the consequences of the absurd lust after kings to rule over them. This afforded Paine an excellent chance for prepossessing the colonists in favor of republican institutions and instilling into their minds a prejudice against the king as being the "anointed of the Lord."
He also ridiculed the idea of a vast continent like America being in a state of vassalage to a small island like England. This stung the pride of the Americans and more thoroughly convinced them as to the propriety of renouncing the assumed right of the British to rule them. Probably nothing could have happened at a more opportune time. The pamphlet was addressed to a body of men who for several years past had received convincing proof that Great Britain cared for them only because of the benefits derived; that she desired to compel submission to any measures, despite all opposition on the part of the colonists; and that she would not spill the blood of her own sons to compel obedience, but had taken the dishonorable course of hiring foreign bullies. Consequently, many of the colonists who had previously been lukewarm in their adherence to the American cause, now became ardent patriots, while a large number who had really been attached to the royal cause became very lukewarm in their allegiance to the king.