An Introduction to John Locke

Austin Tannenbaum
10 min readMay 24, 2021


John Locke was an English philosopher from the 17th century whose writings revolutionized both epistemology and politics. His tabula rasa theory of the mind as a blank slate popularized the modern empiricist notion that all knowledge is derived from experience, while his writings on freedom and tyranny informed the Declaration of Independence.

Locke was born August 29, 1632 in the pastoral town of Wrington, England and brought up in a Puritan family. His father was a lawyer and served as a military officer for the Parliamentarian forces during the English Civil War. Locke’s father’s commander sponsored Locke’s childhood education, allowing Locke to attend the prestigious Westminster School in London.

After graduating, Locke attended college at Christ Church, Oxford. He was irritated with the school’s curriculum, preferring to read contemporary philosophers rather than the ancients assigned. Nonetheless, Locke obtained his bachelor’s degree in 1656 and his master’s in 1658. Locke remained affiliated with Christ Church for a number of years, holding administrative posts, teaching undergraduates, and studying medicine, earning a bachelor’s degree in the latter in 1675.

In the interim, Locke had lived with Lord Ashley (later Earl of Schaftesbury) and served as his personal physician. Ashley was a prominent member of the Whig movement that opposed absolute monarchy in favor of a parliamentary system. Locke also served as Secretary of the Board of Trade and Plantations and Secretary to the Lords Proprietors of Carolina.

In 1683, Locke was forced to flee to the Netherlands following suspicions (to this day unproven) that he was involved in the Rye House Plot to assassinate King Charles II and his brother James. In the Netherlands, Locke frequently conversed with Spinoza’s disciples, which informed his views on religious tolerance. His time in the Netherlands was also fruitful for his writing; he completed his three major works — An Essay Concerning Human Understanding, Two Treatises of Government, and A Letter Concerning Toleration — while residing there. Following the Glorious Revolution, which ended decades of civil strife in England and established a parliamentary system, Locke was able to return to his mother country and publish his works.

In 1691, Locke became a guest at the Mashams’ house at the invitation of Lady Masham and spent the remainder of his life there. Following a lifetime of respiratory illnesses, Locke passed away in 1704. He never married or had children.

Locke’s philosophical system begins with a Cartesian investigation of the self. In the introduction to the Essay, Locke claims that our advanced understanding is what separates us from the rest of the animal kingdom. But while our understanding easily affords us knowledge of external things, gaining knowledge about the understanding itself is a difficult task that requires work. Locke suggests that before we can accurately understand the world, we must understand ourselves and how we apprehend it. Moreover, we must understand the limits of our understanding, so we can distinguish between questions that are appropriate to undertake and those that lie beyond our ken. Locke reassures us that it is alright to lack the ability to understand everything perfectly, as we are able to know more than enough “for the conveniences of life, and information of virtue.” In keeping with this, he advocates humility and gratitude, admonishing against “boldly quarreling with our own constitution, and throwing away the blessings our hands are filled with, because they are not big enough to grasp everything.” Instead, he reminds us in a poetic analogy that “it is of great use to the sailor to know the length of his line, though he cannot with it fathom all the depths of the ocean.”

Locke’s model of the understanding centers on ideas, which he defines as “the object of understanding when a man thinks.” In other words, ideas are the contents of our consciousness. Locke identifies two categories of ideas:

  1. Simple: singular ideas received through the senses, such as wood.
  2. Complex: composite ideas made up of two or more simple ideas, such as an upholstered chair.

While simple ideas all have the same form, complex ideas are said to take three different forms:

  1. Substances: ideas that exist as an independent category, such as a house.
  2. Modes: ideas that exist as sub-types of substances, such mansions, cottages, ranches, etc. in reference to types of houses.
  3. Relations: ideas that describe relationships between things, such as landlord, tenant, owner, realtor, etc.

Unlike simple ideas that are directly perceived, complex ideas are constructed by the understanding in the following three ways:

  1. Combining two or more ideas into a compound.
  2. Studying the relations between two or more ideas; comparing and contrasting.
  3. Generalizing ideas: abstracting them from their “real existence” and analyzing them theoretically.

As is suggested by this framework, Locke holds that ideas are derived from two kinds of experiences:

  1. Sensation: sensory observations of the external world.
  2. Reflection: applying cognitive processes such as reason, judgment, and synthesis to sensory ideas to draw out new ideas.

Locke asserts that all knowledge is derived from experience. That is to say, we are blank slates with no innate ideas, and only acquire ideas once we begin perceiving and reflecting on the world. Against his critics, Locke argues that no idea, not even logical proofs such as A = A, are universally held, being allegedly lacked by “children, idiots, savages, and illiterate people.” Importantly, Locke distinguishes between our capacity to possess ideas, which he affirms, and our actually possessing them from birth, which he denies.

Locke’s model of knowledge acquisition is thus roughly as follows:

  • First, our senses “let in particular ideas, furnishing the yet empty cabinet.”
  • Next, these ideas are “lodged in the memory” and assigned names.
  • Finally, the reflective mind compares newly received ideas to preexisting ideas and determines whether they are able to coexist in a logically consistent manner.

Ultimately, Locke admits that we cannot know with certainty, as we are unaware of what matter is really made of, and thus lack perfect knowledge of objects. Imperfect knowledge nevertheless helps us navigate the world, and is therefore useful and worth pursuing. Locke contrasts knowledge, which is demonstrated agreement between ideas, with opinion and belief, which merely presume agreement between ideas. Locke was a proponent of Enlightenment skepticism and the scientific method, challenging humanity to overcome its personal biases and embrace reason. He famously declared that “whatever I write, as soon as I discover it not to be true, my hand shall be the forwardest to throw it into the fire.”

Locke had no qualms about throwing others’ ideas into the fire if they did not stand up to scrutiny. In the first of his Two Treatises of Government, he rejects his contemporary Robert Filmer’s argument that kings, as descendents of Adam, have exclusive right over the world and its governance. Locke points out that there is no reliable way to trace Adam’s descendents to the present; but more importantly, that “natural right” entitles everyone to the world. Locke’s reasoning is partly biblical: in Genesis, God is said to have given all humans dominion over the Earth. However, in Hobbesian fashion, Locke also offers the secular argument that humans, being roughly equal in ability, are all entitled to try to survive, and to utilize the world and its resources as a means to do so.

Locke is more optimistic about human nature than Hobbes, who maintains that in a state of nature, competition for limited resources leads to a “war of all against all.” On the contrary, Locke suggests that to avoid conflict and increase our chances of survival, it is in our collective interest to treat one another well, so we typically do. Put differently, the golden rule is a mandate of reason: since I desire peace, I should act peacefully; since I desire respect, I should act respectfully toward others, and so on.

This rational reciprocity encompasses respect for others’ life, liberty, and property. With regard to the latter, Locke suggests that since humans have a right to attempt to survive, everyone has a right to the provisions that afford survival: food, water, shelter, etc. Locke distinguishes between raw materials, which exist in nature, and property, which requires human labor to produce. While everyone has a right to natural resources, the laborer is said to have exclusive right over their property by virtue of producing it.

According to Locke, it is appropriate for one to parlay natural resources into property only to the extent that they can actually use what they’ve produced. If, on the other hand, the property goes to waste, e.g. if excess food spoils before being consumed, it is an “offense against nature.” This rule is said to have governed property relations until the advent of money, which allowed individuals to exchange their excess property for a non-perishable form of value. In light of this, Locke argues that it is not property that creates inequality, but the introduction of a currency, which allows individuals to accumulate surplus value. At this point, a state of nature is no longer enough to ensure harmony among individuals, as the complex economy of a money society cannot be governed by individuals alone. Instead, individuals require formal laws and an external body capable of enforcing them to establish property rights, arbitrate disputes, and strike a balance between capital accumulation and social equality. Seeing the benefits of such an arrangement, individuals mutually agree to relinquish some of their natural freedom to a government in exchange for security and protection in the proverbial “social contract.”

Unlike Hobbes, Locke holds that the social contract must be engaged in voluntarily; all other forms of government are illegitimate. His reasoning is that since humans are created free, the government must obtain consent before it can rule over a people. Taking it a step further, Locke argues that a contract only holds so long as the government acts in accordance with its citizens’ interests. As soon as it ceases to, either through tyranny or neglect, the citizens have the right to overthrow it — a principle embraced by the American colonies when declaring independence from Britain. Locke also opposes Hobbes’s view that monarchy is the best form of government. Finding humans to be subject to personal biases that cause them to be lenient with themselves and their friends and strict with those they dislike, Locke warns that absolute monarchy allocates too much unaccountable power to one person. Locke envisions a government of laws rather than a government of men in a majority-rule arrangement approximating a democratic republic.

Another pillar of Locke’s political system is the separation of church and state — perhaps a truism in the contemporary West, but a radical idea for its time. Locke was a religious man, upholding the cosmological argument (that there must be a first creator to explain all subsequent creation) as a logical proof of God’s existence and rejecting atheism as a practice leading to moral decay. However, for both individual and social reasons, Locke advocated religious tolerance. In A Letter Concerning Toleration, Locke argues that as humans with imperfect knowledge, we cannot reliably evaluate the truth claims of different religions, and so ought to permit individuals to ascribe to whichever religion they wish. He also points out that a government’s job is to regulate the public sphere rather than the private sphere, which places religious practice outside the government’s jurisdiction. Additionally, Locke asserts that coercing religious uniformity — which provokes violent opposition — leads to more social disorder than permitting religious diversity, and that since a government’s job is to maintain peace and stability, it must therefore practice tolerance. Finally, Locke indicates that belief is not compelled by force, but entered into voluntarily, rendering the project of religious conformity a futile endeavor.

While Locke opposed subjugation of any kind — religious or otherwise — in his writings, he participated in it in practice. Despite describing slavery as a socially sanctioned “state of war,” he invested in the slave-trading Royal Africa Company and helped draft the pro-slavery Fundamental Constitutions of Carolina, which gave “every freeman of Carolina…absolute power and authority over his negro slaves.” Locke’s contradictory position foreshadowed the colonies’ betrayal of the Declaration of Independence (that “all men are created equal” and “endowed with unalienable rights”) by continuing to practice slavery. This remains a major blemish on Locke’s record and raises the question of whether it is possible to separate the textual Locke from the man and his actions.

Returning to Locke qua theorist, it is worth mentioning that he was a proponent of free will, maintaining that as conscious beings, we have the ability to act rather than merely be acted upon. Locke endows us with agency to control our actions, reflect, and make decisions, with a couple of caveats. First, we may act freely only when the act is capable of being both willed and performed. Second, Locke acknowledges that most of the time, the will is determined by “uneasiness”: the absence of something that we wish to be present, which causes the will to reflexively attempt to secure it. That being said, because humans possess the capacity to reflect, we can stop ourselves from acting on our uneasiness and instead chart a different path.

Whether or not we actually do, however, is said to be a product of our upbringing. In Locke’s words, “of all the men we meet with, nine parts of ten are what they are, good or evil, useful or not, by their education.” Locke places great emphasis on early childhood, stating that “the little and almost insensible impressions on our tender infancies have very important and lasting consequences.” This is because our first experiences, converted into ideas, form the basis of our understanding about ourselves and the world; they are the foundational marks on the so-called tabula rasa. Locke had an admirably progressive educational philosophy, rejecting corporal punishment and identifying practical instruction and self-discovery as the most effective ways to help children internalize intellectual and moral lessons. His hope was that through this enlightened pedagogy, society would produce enlightened individuals willing to carry out his democratic, tolerant vision for the modern world.