(also called Certainty).— 1. Subjective Certitude. A firm assent of the intellect. 

Merely Subjective Certitude.— Certitude that is unjustified, i.e., not based on sufficient motives. 

Formal Certitude.— Certitude that is justified, i.e., based on motives, whether of authority, signs, probability, or demonstration. 

Physical Certitude.— Certitude of evidence (or of intrinsic evidence) regarding the laws that govern the material world, i.e., laws that, strictly speaking, can be otherwise but that there is no reason to expect to be otherwise, e.g., the law of gravity.  This division of certitude plays a particularly important role for those who emphasize (and sometimes over-emphasize) the scope of God’s potentia absoluta. 

Probable Certitude.  Certitude based upon weighty intrinsic evidence or upon the external evidence of authorities.  Probable certitude involves a real inclination toward the truth and, technically speaking, is marked by “probabiliority” or the property of being “more probable” than other options.  Although such certitude does not fully remove the fear of error, it plays an important role in the progressive growth of certitude while considering a given subject matter.  Insofar as such certitude is an inclination toward truth (though with a fear of error), it should be distinguished from a doubt, in which the intellect is not inclined toward any particular truth more than to another. 

 
Prior to the debates over moral probabilism, such probable certitude was said to drive out other non-probable opinions.  During the probabilist debates, many held that one could simultaneously have probable certainty about a number of judgments at one and the same time. Such an understanding of probability marked a new conception, differing from the classical notion thereof. 

Moral Certitude.— Certitude of evidence (or of intrinsic evidence) regarding general habitual human conduct, i.e., conduct that, strictly speaking, can be otherwise but that there is no reason to expect to be otherwise, e.g., that a mentally stable person will not physically assault a friend without provocation.  This is a division of probable certainty.  The term “moral certitude” is most often found in modern texts, not classical ones. 

Metaphysical Certitude.— Certitude of evidence (or of intrinsic evidence) regarding that which, strictly speaking, cannot be otherwise, i.e., that which is absolutely necessary, e.g., the principle of non-contradiction.   Like physical certitude and moral certitude, this division is modern and does not completely correlate to more classic divisions of certitude.  Such “metaphysical certitude” could also be referred to as absolute certitude, either in the form of immediate self-evident principles or mediate demonstrative conclusions drawn in light of such principles.   

Certitude of Faith.— Formal certitude regarding matters reported to us by reliable authorities or witnesses. This can be natural faith or supernatural (divine) faith. When it is natural faith it is sometimes regarded as a kind of probable (or, according to modern terminology, moral) certitude. Some philosophers understand faith to be a kind of extrinsic evidence. 

2. Objective Certitude.— The thing that motivates certitude in a person; that about which one is certain.