Can The Devil Read Our Minds?

The short answer: No.

The long answer: Well, he's capable of doing other related things of which we need to be aware.

Here, I would like to focus on what demons can do that is similar to, but not the same thing as, reading our minds.

Many years ago, when studying for my Masters in Theology, I learned the refreshing truth that demons are not capable of reading our minds. For me, this was a tremendous realization, as I had, up until that point, thought the opposite.

That opposite way of thinking contributed to my insufficient understanding of how the diabolical functions in the world and in its interactions with souls, such as my own. When I realized that my thoughts were safe from the devil, I experienced a great degree of freedom. However, simply knowing that the demons cannot read our minds is not sufficient either, as they are capable of quite a bit which is similar to this, and which can still impact us in significant ways.

Even though my thoughts are out of view of the demons, my thoughts are not necessarily safe from the demons. 

As I discuss in my book, Slaying Dragons: What Exorcists See & What We Should Know, demons are capable of many things as related to our own private thoughts. They are highly skilled at guessing what we are thinking by a whole host of physical signs and observations. Further, they are also steady at work in their attempt to manipulate us in a variety of ways, such as through our emotions, our memories, our perceptions, our thoughts and beliefs, our interactions with other people, and our attraction to specific virtues and vices.

While our secret thoughts are not visible to the demons, the demons, by their work, can impact what those secret thoughts actually are.

Thoughts vs. Imagination

In my book, I discuss how demons can have access to our memory and imagination. These are distinct from our thoughts, from our "mind," in the sense of "reading our mind." However, the devil can stir the imagination, stir the passions, insert imagery into the mind, trigger memories, whisper suggestions – and these either directly or indirectly impact our own thinking.

Though that is a lot of influence, the demons still cannot see what we are thinking. They can only watch us to conclude what we are thinking, and then proceed to interact with us again, in our minds, by the techniques just mentioned.

Along the way, they poke and prod, suggest and observe, watch from near and afar. Demons will then proceed with their temptations based on what they think that we are thinking. This can proceed like a trial and error technique, for which they have plenty of time.

They eventually develop an understanding of how we think, based solely on our habits and our responses to the things they are doing in secret. Since temptations are very often indistinguishable from our own thoughts, they are able to hide in this obscurity and continuously work at manipulating the way we think and act.

The Teachings of St. Thomas Aquinas

The rest of this article will rely heavily upon the luminous teachings of St. Thomas Aquinas. As readers of this blog will know, St. Thomas is the “Common Doctor” whose teachings are a true standard for understanding Divine Revelation. Pope Pius XI, among other Popes, praised this great saint with fitting eloquence in his encyclical “Studiorum Ducem,” which you can read here.

As a result, what St. Thomas says is a sure foundation from which we may proceed to develop and mold our own understanding of how things work. On the matter of the diabolical, St. Thomas has offered us quite a bit of wisdom. On the specific issue of whether demons can read our minds, let us now consider what he says in this regard.

Angels can influence the minds of men. Can demons?

St. Thomas teaches that angels, as the higher beings in God’s creation, can enlighten men, who are the lower beings. This is how God structured the order of His creation. Unlike angels, men are not able to understand univeral truths directly, but must be given explanations of these things through a comparison to sensible objects which we can see in the visible created order. When angels enlighten men, they propose certain truths to us through the use of images we have in our minds, which are based on sensible objects we percieve in the world. St. Thomas calls these images “phantasms.”

Phantasms are an important element to reflect on, as they are the “matter,” so to speak, which the demons can interact with and act upon.

These phantasms reside in the imagination, the memory, and the cogitative power. (Contra Gentiles, 73.14) As exorcists notice and teach, demons, as said above, are capable of interacting with our memory and imagination. This is explained by St. Thomas as an interaction with the phantasms that reside there. These phantasms can included sounds and sights that we have experienced, which the demons can stir up, replay, or represent with a distortion.

St. Thomas further teaches that, since the body of man can be moved by the spiritual nature, the devil, God permitting, is also capable of producing “all those effects which can result from the local movement of bodies here below.”

Thus, demons produce many effects in the body, which will in turn affect the way we think, if we are not discerning and virtuous.

Can demons put thoughts into our minds by causing them internally?

In St. Thomas says that demons are not capable of putting thoughts in our minds in that way because the faculty of the soul that does this is subject to the will of the individual, which the demon cannot control.

Nonetheless, St. Thomas points out that the devil is still referred to as the “kindler of thoughts, inasmuch as he incites to thought,” causing us to think certain things. He does this through stirring desire for the thing thought about, through persuasion, or through stirring the passions. St. John Damascene refers to this as “putting in” a thought because this work of the devil is done from within the person.

The Imagination

St. Thomas states,“Both a good and a bad angel by their own natural power can move the human imagination.”

He adds that “the operation of the devil seems to be confined to the imagination and sensitive appetite,” through which, by stirring them, he can induce us to sin. The devil can “present certain forms to the imagination” and “incite the sensitive appetite to some passion or other.” The devil’s intention with man is to darken his reason so he will consent to sin. This “darkness is due to the imagination and sensitive appetite.”

The Passions   

St. Thomas teaches that the devil can cooperate in inciting the passions within a man. These passions can put sensible images before the imagination which are then judged by the man to be something he should pursue. This is because the man who is held captive by, or is weak to, a certain passion, deems to be good whatever that passion suggests to him.

By inciting these passions, the devil can inwardly incite man to sin and to think in a way that is sinful and contrary to truth.

A Note on the Sensitive Appetites

The sensitive appetites are desires that flow from the senses of the body when an object is understood to be useful or pleasurable. These appetites are divided into the concupiscible appetite and the irascible appetite. The manifestations of these appetites are referred to as “passions,” as mentioned above. As the Catholic Encyclopedia says, “There are six passions for the concupiscible appetite: love and hatred, desire and aversion, joy and sadness; and five for the irascible appetite: hope and despair, courage, fear, and anger.”

The Senses  

St. Thomas says that, in the normal course of things, a man’s senses may be changed in two ways, either from the outside, through some sensible object, or from within, when the senses are changed by some disturbance, as the tasting power of the tongue can be disturbed by sickness. The natural power of an angel gives the angel the ability to change a man’s senses by both means.

Regarding sensible objects, the good angels can do this when they use objects already formed by nature, or when they choose to assume a body in order to communicate with a man. The bad angels, as has been observed by priests and exorcists, can also do this, such as when they infest homes, impacting objects in the process, and when they manifest as solid black forms.

Regarding internal disturbances, both the good and bad angels are capable of doing this, as seen when the angels in Sodom blinded the evil men, and when St. Raphael healed Tobit of blindness. In addition to the above mentioned internal disturbances, demons are also capable of inflicting illnesses upon men, which are not due to a natural cause, and are resolved by the Sacraments, sacramentals, exorcisms and deliverance prayers.

The Use of Reason  

St. Thomas says that the devil is capable, by the power of his nature, to compel a man to do an act which is of a sinful type, but he cannot actually compel the man to sin. The man can resist the movement toward this sin by his use of reason.

However, the devil is capable of impeding the use of reason by moving the imagination and the sensitive appetite. St. Thomas says that the devil’s ability to “impede altogether” the use of reason is seen in the case of one who is possessed. So long as “the reason is not altogether fettered” or restrained or impeded, then “in so far as it is free, it can resist sin.” The movement of the imagination and the sensitive appetite by the devil also leads to the darkening of reason, as stated above, which leads man to sin.

When the man does consent to sin, it, as Our Lord teaches, places him in a state of slavery to sin and to the devil.  St. Thomas points out that slavery can come about when a man subjects himself to another spontaneously. This occurs when the man “sins of his own accord.” That man then “becomes the slave of the devil.”


Though the demons are not able to have access to our thoughts, or to cause thoughts for us in our mind, they are capable of a good deal of influence which can subtly and surreptitiously change the way we think. Demons are permitted to have access to our memories, our imaginations, and the images with which we interact to make decisions and reflect on our course in life. This ability flows from their nature which, while impacted by the fall from grace, retains its natural powers.

This influence can be referred to as a form of harassment of the mind which, if we are weak, vicious, or slaves to sin, will easily lead to a manipulation of our thoughts and choosing power. Though they cannot cause thoughts, they are capable of kindling thoughts. The weakness of the flesh provides much of the power that they wield against us, as it is through the weak passions that they disturb us and incite us to think and act in certain ways. All of this effort leads man’s intellect and reason into darkness by which it no longer revolves around truth but the lies which it believed as a result of these actions of sin, both from the devil and from the weak and undisciplined flesh.


Take courage, for we have all of the means, both sacramental and philosophical and ascetical, to block the work of the diabolical. But, as their efforts are ferocious, so must ours be against the disorders in our nature.


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