in order that a right may exist, it is necessary for volition to spring from an intellectual act of understanding, and that understanding must in turn be derived from truth itself. For the ancients were not unjustified in defining law as “right reason.” Those persons, moreover, who give the command for war, are properly admonished not to employ this last weapon of necessity unless such a course of action is based upon just cause.e Cicerof has said: “Those wars are unjust which have been undertaken without cause.”
Now, every right that we possess may be referred to one of four laws: the First, the Second, the Fifth, and the Sixth. For the Third and Fourth Laws, when interpreted from the standpoint of personal welfare, differ not at all from the First and Second, save only in the fact that the terms are reversed; while the Seventh, and all of the laws following thereafter, may be traced back to the Sixth (with the support, that is to say, of the Third Rule). Therefore, every [just] war must have its origin in one of four causes.
The first of these is self-defence, which is based upon the First Law. For, as Ciceroa observes, “. . . the act [of homicide] is not only just but even necessary, when it represents the repulsion of violence by means of violence.” Many statements to the same effect are to be found in the works of various authors.
A second cause is defence of one’s property, based upon the Second Law,b which makes it permissible not only to offer resistance but also to dispossess others. Moreover, the term “property” is to be understood not exclusively in a material sense, but as referring to every right, including that right to a good name which is justly the possession of virtuous persons and of which they ought by no means to be deprived.
A third cause—one that a great many authorities neglect to mention—turns upon debts arising from a contract or from some similar source. To be sure, I presume that this third group of causes has been passed over in silence by some persons for the reason that what is owed us is also said to be our property.c Nevertheless, it has seemed more satisfactory to mention this group specifically, as the only means of interpreting that well-known formula of fetial law:d “And these things, which ought to have been given, done or paid, they have not given, paid or done.” Plato, too, in the Alcibiades,e has said that wars are waged not only when one suffers oppression by violence, or despoliation, but also when one has been deceived. Yet again, the statement made by Senecaf may be cited: “Even cities bring charges against cities on the basis of services rendered.” Moreover, Baldusg expresses a similar view regarding pecuniary debt. [30]
The fourth cause arises from wrongdoing, and from every injury—whether of word or deed—inflicted with unjust intent. Augustineh wrote: “Just wars, indeed, are wont to be defined as those which avenge injuries. Accordingly, that people or state should be attacked, which has neglected to punish evil conduct on the part of its citizens, or to restore what was unjustly taken away.” 30 a]
Now, I wish to have it understood that these four causes listed as suitable subject-matter for war, are of the same character whether the war be private or public. In the case of public wars, however, the rights as well as the examples involved are more clear-cut; and private wars furthermore differ from public wars with respect to their efficient agents and their form. Nevertheless, they are not different in their subject-matter. The examples afforded by all living creatures show that force privately exercised for the defence and safeguarding of one’s own body is justly employed.a Furthermore, such force is also just when the purpose is defence or recovery of one’s property;b nor is it less so when employed for the collection of a debt.c Even private exaction of a penalty for crime is sometimes permitted: for example, when the penalty is imposed upon adulterers (in certain cases), robbers, rebels, or deserters.d It was for this reason that Tertulliane said: “Every man is a soldier against persons guilty of high treason, and against public enemies.” Nor is it by mere chance that the very lawsf expressly apply the term ultio [meaning primarily “vengeance”] to an “indulgence” that has been granted. [30 a′]
On the other hand, even as certain private wars are just by virtue of their cause, so public wars are unjust in the absence of due cause.g Thus Senecah complained: “We put a check on homicide and isolated cases of murder. But what of wars and the boasted crime of slaughter inflicted upon whole nations? Neither avarice nor cruelty recognize any bounds. [. . .] savage acts are committed in accordance with decrees of the Senate and the popular assembly, and the performance of deeds forbidden to private individuals is commanded by public authority.” Cypriana follows Seneca, saying: “When single individuals indulge in homicide, that is a crime. When homicide is committed by public authority, it is termed a virtuous act.” Herein lies the origin of the saying, “And law was given for [the service of] crime.” Accordingly, King Alexander was rightly included by the pirate among the latter’s partners in crime, if that ruler had no just cause for war against Asia; and in this same sense Lucanb called Alexander the “plunderer” of the world, while Senecac described him as a “robber.” A similar view may be taken of Crassus’ war against the Parthians.
New explanation
Therefore, in both kinds of warfare, [public and private,] one must consider the causes involved. Of these there are four kinds, as we have pointed out: for the authorities who hold that there are three just [30] causes of ward (defence, recovery, and punishment, according to their classification), fail to mention the not uncommon cause that arises whenever obligations are not duly discharged. Indeed, in so far as we are concerned with subject-matter, which is the same in warfare and in judicial trials,e we may say that there should be precisely as many kinds of execution as there are kinds of legal action. To be sure, legal judgements are rarely rendered in consequence of causes of the first class, since the necessity for defending oneself does not admit of such delay; but interdicts against attack properly fall under this head. The actions relating to property which we call civil claims, arise from the second kind of cause, as do also injunctions obtained in behalf of possession. The third and fourth classes give rise to personal actions, namely, claims to restitution, founded upon contract or upon injury.
Even as in the case of a lawsuit, however, so also in war, those causes which would justify the action taken by the plaintiff if they were genuine, serve instead to place the accused, or defendant, in the right if they do not have that just character which is claimed for them. For example, if a claim is presented against us for property that is our own, or if we are pressed to do something that we are under no obligation to do, or if it is demanded that we be given up for punishment when we are innocent, then, since the action against us is unjust, the defence must necessarily be just, in accordance with the First Law.
Furthermore, in these disputes involving war just as in the courts of law, not every rightful claim comes into existence before the process of execution. For the execution of one’s right in itself constitutes a right, a point already touched upon in our discussion of prize and booty.a
Accordingly, it is apparent from the foregoing comments that arms are not justly taken up for the sake of undue dominion or liberty,b whereas, for the purpose of rightfully retaining dominion and liberty already acquired, not even war should be shunned. Nevertheless, we should see to it (although this is a matter not so much of right as of discretion) that we do not rashly allow ourselves to be aroused by comparatively trifling injuries; for it is frequently less of a hardship to tolerate these, than it would be to endure the conditions that inevitably accompany war. We must steer clear of Charybdis without falling upon [30′] Scylla. Of a similar character is the forensic principle that it is not necessarily expedient to enter into litigation on every occasion when it is just to do so.
Our remarks on the subject of rights are applicable no less to allies than to the principal authors of a war,c since allies, too, should take care lest they involve themselves in a war that is not just. For they are not compelled to
