Tertullian, along with Justin Martyr and Irenaeus, is seen as one of the founders of Christian apologetics. Tertullian’s main apologetical writing is the aptly named Apology, and this first text offers great insight into the way in which he interacted with the world outside Christianity.

One of Tertullian’s chief assertions made in this text is the notion that most of the hostility towards Christianity is derived from an ignorance of it and that those who become acquainted with it soon find themselves converting, thus he asserts: “By simply getting acquainted with it, they begin now to hate what they had formerly been, and to profess what they had formerly hated.” Much of Tertullian’s Apology is directed at arguing against the more moral – as opposed to intellectual – criticisms that were being railed against Christianity. Thus he defends Christianity against accusations of such things as treason and child sacrifice, and points out the inconsistencies which surround the trials and persecutions of Christians.

After defending the morality of Christianity and addressing unjust persecutions, Tertullian goes on to a more rational defense of Christianity and does so in some creative ways (though many of these are no longer forceful in the modern context). One of these ways is through a proof from the pagan gods.

Tertullian argues that since the pagan gods were once men, they must have been made gods by somebody higher than themselves, thus: “you must concede the existence of one higher God – a certain wholesale dealer in divinity” because “if they could have deified themselves, with a higher state at their command, they would have never been men.”

He argues again from pagan gods to a true God by arguing that since the ‘gods’ show favor to both those that worship them and those that do not, there must be some higher “dispenser of kingdoms, who is Lord at once of the world which is ruled.” Another set of arguments employed by Tertullian are arguments from the antiquity and the majesty of Scripture, that antiquity claims authority and the majesty of Scripture proves that it is divine. Tied in with this is an argument from the demonstration and truth of prophecy presented in Scripture which “is the demonstration of its being from above.” 

It can be observed from the arguments presented by Tertullian here that he is willing to offer counterarguments to criticisms of Christianity as well as a certain sort of argument for Christianity. This is perhaps at least one reason why Tertullian’s approach is seen as a forerunner of the Reformed approach to apologetics, in which “the focus will tend to be on the negative or defensive” side.

Another of Tertullian’s apologetical writings is The Soul’s Testimony. The argument here differs from that presented in the Apology, although it is alluded to in the Apology with the question “Would you have the proof from the works of His hands, so numerous and so great, which both contain you and sustain you… or the testimony of the soul itself?”

Rather than argue from pagan philosophy he aims to “prove the existence of God from the testimony that any man’s soul, whether Christian or not Christian, will give.”  Thus Tertullian asserts that “There is no a soul of man that does not, from the light that is in itself, proclaim the very things we are not permitted to speak above our breath” and “Thou proclaimedst God, O soul, but thou didst not seek to know Him.”

This sort of approach is much different from Tertullian’s other arguments. Rather than defending against attacks or offering an argument from the culture of the pagan, Tertullian here gives a somewhat more existential or psychological argument, appealing to the soul’s desire to worship and render service to something above itself and to “name the name of God” as proof of there being something above itself. While this form of argumentation may take Tertullian closer to the accusation of fideism than does that presented in the Apology, his argument is not based on nothing more than the indwelling of the Spirit and thus he is still arguing from experience rather than asserting the need for a leap of faith.

Again, Tertullian’s apologetic doesn’t seem to be in sharp contrast to reason as such. 

Another sort of apologetic which is often attributed to Tertullian is argument from absurdity, or to put it another way, the argument that the foolishness of the Christian position proves that it could not have been created by human beings and that therefore it must have been divinely constructed and inspired. This is an apologetical method which is not dead in contemporary apologetics; C.S. Lewis makes the same argument in his classic text Mere Christianity, arguing that “It is a religion you could not have guessed… it is not the sort of thing anyone would have made up.”

While this is an argument that is still alive today it is less certain whether Tertullian actually meant this by the statement “it is by all means to be believed, because it is absurd.” Tertullian does not seem to use this argument to argue directly that it could not have been created by man and is therefore divine, but is rather arguing that the ways of God are beyond man, and therefore the things he does may seem foolish to man.

The former may be inferred from the latter, but it does not seem to be directly entailed in it – nor does Tertullian state the former outright – and even when he is discussing the foolishness of the incarnation he does so by explaining how Christianity wouldn’t make sense if not for the foolishness, which is in itself a paradoxical acknowledgement of Christianity’s reasonableness.

If Christ was not flesh he could not have died (and must also therefore have been born), yet he is also God: “Thus the nature of the two substances displayed Him as man and God.” His proof also seems primarily set in the authority of Scripture which asserts that “God hath chosen the foolish things of the world to confound the wise,” arguing that it is therefore believable for God to act in ways that seem foolish to man.

While this argument comes in the context of a dispute against Marcion over the incarnation of Christ, and while it seems to rely highly on Scripture as a proof (unless the modern revamping of the argument is seen as being intended), the argument still gives some insight into Tertullian’s view of philosophy via his apologetic. As is noted by Timothy Barnes, one of Tertullian’s main issues with Marcion was that he was rejecting the incarnation in order to satisfy the conventional standards of his day; thus, Tertullian is in actuality “contrasting the assumptions of Christianity with those of pagan society.”

In a discussion of Tertullian’s apologetic it is also of note that he alludes in various places to a sort of potential natural theology, but argues that such knowledge is taken by philosophy and “inflated with straining after that facility of language which is practiced in the building up and pulling down of everything.”

This contrasting of the assumptions of Christianity with those of pagan society and Tertullian’s critique of what philosophy does with what might be called ‘common grace’ leads well into the discussion of Tertullian’s overall attitude towards philosophy.

There is no shortage of criticism for philosophy in the writings of Tertullian. One of Tertullian’s divisions between Christianity and philosophy comes in his Apology where he points out that when Christians depart from the faith morally, they are no longer considered Christians, whereas “philosophers who do such things retain still the name and honour of wisdom” which leads him to ask “So, then, where is there any likeness between the Christian and the philosopher?”

This division isn’t one between reason and faith, but between a system which is built upon a morality and one that is not.

In this same text Tertullian attacks the philosophers for having perverted both the old Scriptures and the newer revelation, corrupting them “into a system of philosophic doctrines.” Tertullian makes this same sort of attack again in Ad Nationes, making the point that the philosophers take the truth of Scripture and “degenerated [it] into uncertainty.” Here he adds that “For after they had simply found God, they did not expound Him as they found Him, but rather disputed about His quality, and His nature, and even about His abode”

A final repetition of this outcry can be found following the oft-quoted “What indeed hath Athens to do with Jerusalem” in Tertullian’s On Prescription Against Heresies. Here he calls philosophy that which “pretends to know the truth, whilst it only corrupts it” and cries “Away with all attempts to produce a mottled Christianity of Stoic, Platonic, and dialectic composition!”

In this Tertullian is not so much railing against reason as such, but against philosophers who combine their philosophies with Christianity, against individuals who attempt to force Christianity to adhere to some preconceived system, and who distract themselves from the truth of God by quarrelling about various aspects of God apart from what is presented in Scripture and who debate the same questions over and over such as “why is evil permitted” in the course of tearing down the doctrines.

It may thus be said that Tertullian’s arguments against philosophy were not against rationality per se or of considering philosophic issues “but of the pagan philosophies that took their point of departure in human speculations.”

If Tertullian’s apologetic employed various sorts of proofs and defenses and if his critique of philosophy was chiefly built around keeping philosophers from modifying Christianity to suite their systems, it must still be inquired as to Tertullian’s direct view of the relationship between faith and reason.

From his apologetic it can already be seen that he posits various arguments which aim to make Christianity reasonable, and from his treatment of philosophy it can be observed that he did not critique them simply for their use of reason.

Still, Tertullian does distinguish the knowledge of revelation and faith from that of reason and human wisdom.

In looking back at Tertullian’s apologetic it can be seen that after he defends Christianity against the accusations of the pagans he goes on to spell out just what Christianity is. This in itself is part of his apologetic, as can be inferred by his earlier statements that the main barrier between pagans and Christianity is ignorance of it.

Once Tertullian begins explaining what Christianity is he notes that God is incomprehensible “though in grace He is manifested” and again that “He is beyond our utmost thought, though our human faculties conceive of Him. He is therefore equally real and great.”

It seems from such statements as this that Tertullian at the very least sees Christianity as being a reasonable faith.

Despite this, it may also be observed that Tertullian does not view it as a faith which can be reached by reason alone. As has already been observed he had very little confidence in what philosophy did with the things of natural revelation. Tertullian perhaps best surmises his view in A Treatise on the Soul, where he states that:

“For by whom has truth ever been discovered without God? By whom has God ever been found without Christ? By whom has Christ ever been explored without the Holy Spirit? By whom has the Holy Spirit ever been attained without the mysterious gift of faith? From God you may learn about that which you hold of God; but from none else will you get this knowledge, if you get it not from God.”

Thus faith is an absolutely integral factor for in regards to knowledge for Tertullian, for without it God cannot be discovered, much less by the common man.

Indeed, God can be discovered and known without the strain of philosophy or the acrobatics of reason, thus “there is not a Christian workman but finds out God, and manifests Him, and hence assigns to Him all those attributes which go to constitute a divine being” even though God is difficult to find out and difficult to make known.

Rather than viewing Christianity as something opposed to reason or “a faith that is as isolated from reason as possible” as Boa and Bowman suggest, Tertullian seems to view Christianity as something that is reasonable but must be initiated by faith.

It is important to note here, however, that when Tertullian speaks of faith he does not simply mean to put faith in the Scriptures. Rather, he appeals to a rule of faith, which is the successive teachings passed down from the apostles. While this ‘rule of faith’ is derived from Scripture, it does put tradition on a very high pedestal, so much that he recommends using tradition to argue against heretics rather than Scripture or philosophy.

In the contemporary context the question of how to approach secular philosophies and worldviews is just as critical as it was in Tertullian’s day.

If taken outright Tertullian’s position may be seen as a countercultural movement of Christianity against the culture around it, as is pronounced by Neibhur or Alister McGrath when he asserts that Tertullian’s position is one which “refused to allow itself to be contaminated in any way by the mental or moral environment in which it took root.”

Yet Tertullian himself writes with much knowledge of the Platonic and Socratic philosophies, asserts that the truth which the pagans have is derived from Christian writings, and was “deeply imbued with traditional rhetoric.”

At the very least Tertullian gives a sharp warning against syncretism, although it may be going to far to set him distinctly in a Christ against culture camp.

While some of Tertullian’s specific arguments – such as arguing from pagan gods to the true God – may no longer bear any force, his general method is still quite pertinent. Many who reject Christianity still do so while having little idea of what Christianity actually teaches, and Tertullian also offers various arguments which are still around today (even if in modified form). The question of the relationships between Christianity and philosophy or between faith and reason are also just as alive today as they were in Tertullian’s, perhaps even more-so.

Tertullian does well to point out the ways in which Christianity may be perverted by modifying it to fit some preconceived philosophic system, a problem which was present first with classic liberalism and is present still with postmodernism, which seek to cut off the bits of Christianity which do not adhere to their system or what they believe to have truth value.

The current theological and philosophic climate also presents much hostility to the relationship between faith and reason, different groups seeking to place them at different levels of authority. As Etienne Gilson puts it in a more contemporary context, the reason why the universe seems confounded to scientists is that they mistake existential and metaphysical questions for scientific ones, “then they are puzzled, and they say that the universe is mysterious.”

Tertullian does well to point out that it is only through faith that God can be reached, rather than through some rationalistic striving of mankind.

Once that faith is reached, it  may be asserted that the faith is reasonable within its own system, for even when Tertullian calls the doctrines of Christianity foolish he does so in order to paradoxically point out their reasonableness and the way in which both must be accepted in order for the Christian faith and its doctrines to have congruity.

Through analysis of his apologetical method, his thoughts on the relationship between pagan philosophy and Christianity, and his thoughts on the relationship between faith and reason, one may conclude that the one of the key elements of Tertullian’s thought was that “Men are not to determine in advance of meeting Christ what his nature must be” and that knowledge of truth and of God may only ultimately come through the faith which is given by God himself.

The knowledge of God is further augmented by the revelation given to mankind in Scripture; yet Protestants must be wary of the baggage that Tertullian adds onto Scripture, namely, the force of interpretation based on apostolic succession.

He is not merely a fideist, but offers both rebuttals and arguments for the Christian faith – arguments based on the context of the people he is speaking to, based upon experience, and based upon psychology.

Despite writing some eight-hundred years ago, Tertullian’s thoughts still have just as much weight now as they did during his own time, even if the specific arguments and worldviews which are to be defended against have changed.

The essential conflict is still the same, secular philosophies still attempt to pervert the truths of Christianity, though perhaps with Tertullian it might be said “With our faith, we desire no further belief.”