In these political pamphlets Machiavelli formed a new political theory that had been developed through observation of the Italian city-states of the early 16th century where authority depended solely on the cunning and effective use of force.

Medieval governments fused religion and politics:

A.) Machiavelli had no patience with theories that sought to shape political life in accordance with ideal standards. By raising humble and contemplative Christians to high office, society had been plunged into anarchy and confusion. Indeed, he argued that utopian visions would bring ruin to the state. The ruler should do whatever is necessary to protect the state from domestic and foreign threats as well as  the unruly passions of his subjects. Machiavelli admired the classical era whose leaders had valued personal achievement, courage, strength, pride, glory, civic responsibility and patriotism.

B.) Machiavelli had a bleak vision of human nature: men were naturally selfish, corrupt, cowardly, faithless, base, dishonest, and violent. Deception and coercion were necessary to control the human appetite for acquisition and dominance. Only through coercion could a Prince maintain order. 

C.) The state is an entirely natural entity governed by scientific laws. Machiavelli arrived at his conclusions through empirical analysis of data, from the study of historical fact. He freed himself from any illusions about the practicality of ideal societies or divine standards. He was the first political scientist.

D.) "The end justifies the means." All means are permitted the prince if the state's survival is at stake. Machiavelli argued that rulers who tried to govern using compassion and moral good needlessly exposed themselves to violent betrayal. Instead of using moral standards, the ruler should logically analyze the situation and take whatever action necessary to secure his rule. Only in that way could the stability of the state be assured and the safety of the people. Only blunders, not crimes are unpardonable. The wise prince gives the appearance of being good, for such a pretense will help him govern, but when the situation calls for action, he should be prepared to abandon all virtue.

Livy's History of Republican Rome and Plutarch's Lives provided the models for his vision of statecraft and his faith in citizen soldiers instead of mercenaries. Machiavelli tempers his respect for the golden words of the past by subjecting their ideas to practical test in the arena of Florentine politics.

Machiavelli rose to high political position (Secretary in the Chancery) as part of the faction that took power in Florence after the execution of Girolamo Savanarola (1498); for Machiavelli, Savanrola was the epitome of the unarmed prophet doomed to failure. Cesare Borgia, the warrior son of Pope Alexander VI, provided his model for the Prince: a leader of boldness, resolution and cunning. 

In 1512 Machiavelli was arrested and tortured by the Medici when his mentor Piero Solderini was overthrown. Machiavelli was exiled to the country and began his literary career. 

The occasion for the writing of The Prince: the good fortune of the Medici family to have a Pope on the throne in Rome while a family member also controlled Florence and Tuscany. Machiavelli saw an opportunity for the formation of a central government strong enough to resist the unending invasions which kept Northern Italy in a permanent state of war with factions allying with and against each other as they jockeyed for power.

1561 The publication of Franesco Guicciardini's History of Italy redefines the public persona of the Borgias as the incestuous perpetrators of legendary homicides: atheism, treachery, perversion and 'Machiavellian politics'.

Chapters VII-VIII and Chapters XV-XVIII of The Prince (scandalous moral attributes)

Machiavelli's famous dictum "The end justifies the means." is really a misreading of a passage in Chapter 18 in which he argues that one must consider the final result in any political action. He is not justifying any and all actions that serve political ends. At one point in Chapter VIII he describes Agathocles, the tyrant of Syracuse, "it cannot be called virtu to kill one's fellow citizens, to betray friends, to be without faith, without mercy, without religion; by these means one can acquire power but not glory." Rather, Machiavelli argues that a successful leader must at times act outside the boundaries of traditional ethical restraints.

On Romulus' murder of Remus (from The Discourses I, ix): 

"It is indeed fitting that while the action accuses him, the result excuses him; and when this result is good, as it is with Romulus, it will always excuse him; for one should reproach a man who is violent in order to destroy, not one who is violent in order to mend things."

If violence is committed in the interest of the people rather than private advantage, then it is good. 

He half agrees with Pico della Mirandolla that humans rule at least part of their destiny. Fortune smiles like a lady on the energetic and ambitious young man. And the occasion will then arise when a man can take action that not only furthers his ambitions but also leads to a more stable and secure state. Like the occasion that the Medici encounter in 1513.

Machiavelli preferred a republican state, not an authoritarian one, but in the specific context of 1513, and the Medici's opportunity to eject foreign invaders from Italy, he could support the idea of a single authority, a prince.

Machiavelli and Human Nature:

Machiavelli emphasizes the political protagonist in his book, not broader socio-economic forces; therefore, his assessment of human nature is central to his philosophy. He draws a similar picture of human nature as earlier Christian theologians who judged human nature to be corrupt, but Machiavelli drew different conclusions: Machiavelli concludes that human nature is irremediably bad: men are selfish, driven by an insatiable desire for material gain, and cannot be trusted unless that trust is based on fear. Man is also gullible and easily deceived by appearances. Rather than draw pessimistic conclusions about the possibilities for social harmony, Machiavelli argues that this constant and unchanging situation makes it possible to predict and thus control the behavior of people. The use of reason can allow rulers who are mentally tough enough to organize, collect, study and use their understanding of human nature as the basis for wise decisions. An empirical science of politics could be constructed by using reason to evaluate the mistakes of past rulers. He also identified politics with conflict and regarded social conflict of a certain kind as a positive force.

The didactic value of studying human history: 

Renaissance men should 'return to the past' in order to find positive examples. The artistic and cultural renaissance could be extended to the more practical realm of political affairs. He did not believe in progress as we do, influenced by the Enlightenment and the Romantics. The state could become a work of art, the product of conscious social planning on a purely secular level. 

Politics as conflict: 

1. human nature is naturally acquisitive and insatiable in its desires. 
2. fortune prevents most men from having sufficient virtu to obtain all of what they desire: a universal principle of economic scarcity. 
3. Combine both ideas and conflict is the inevitable result. 

Conspiracies, invasions and wars are thus natural phenomena. Such conflict might produce beneficial results in a properly organized government with stable political institutions. Machiavelli sought to refute the traditional claim that a republic was an inherently unstable institution. A mixed form of government was preferable to principality, aristocracy, and democracy which would degenerate respectively into tyranny, oligarchy and anarchy. 

In the Roman Republic, a healthy body politic was characterized by friction and social conflict: the friction between plebeians and aristocrats. He proposed a dynamic equilibrium between these forces rather than a false stability based on repression. 

The inevitability of war: 

the place of military affairs is paramount. Military strength is the paramount virtue: self-sufficiency and the ability to field an army against combined enemies. Good laws cannot exist without good armies. Free republican governments cannot exist without a citizen's militia: a bulwark against tyrannical power and a school to teach civic responsibility and patriotism.

Corruption and civic instability: individual virtu is replaced by social ordini as the key idea: institutions, constitutions and organization of the state. Ancient Rome's pagan emphasis on guaranteeing oaths and instilling courage: religion as a means of political control vs. Christianity's glorification of humility. Concentration of wealth in the few. Factions arise when a private citizen acquires excessive power, influence or wealth and employs it for private ends. Rome developed institutions which channeled the conflict between haves and have nots. 

In Florence conflicts typically arose between members of the same class. Institutions enable the various members of a society to express their interests without resorting to faction. Machiavelli also depended upon the heroic action of an individual leader to safeguard the interests of the society as a whole rather than his personal ambition or the success of an individual faction. Machiavelli supported the idea of using a dictator with unlimited powers as long as he did not seek to modify the ordini of the state or seek an unlimited time in power. Republican institutions are unsuited to dealing with rapidly developing problems such as an invasion, so a dictatorship is merely a safety valve to safeguard republican institutions.

Summary:
First: a political thinker who established the theoretical autonomy of politics, separate from ethics and theology.
Second: the first empirical political scientist, as influential as Galileo in his own field.