Total Depravity is part of the Five Points of Calvinism and is represented by the letter T in the word TULIP:
Read more about the distinctive Reformed view of total depravity in this excerpt from the second chapter of Saved by Grace by Ronald Cammenga and Ronald Hanko.
The doctrine of total depravity is the first of the Five Points of Calvinism and is represented by the letter T in the memory-help TULIP...
This doctrine is sometimes called "total inability," emphasizing correctly sinful man's inability to do good. This label, however, is deficient in one respect. It describes man's wickedness only as a lack of good, forgetting that the opposite is also true. Sinful man not only lacks good but is actively and willingly evil. Since the word "depravity" emphasizes this, total depravity is the better name.
When we describe man's sinfulness as depravity, we are not just saying that he is bad or wicked, but that he is rebelliously and deliberately evil, that he loves and delights in wickedness of every kind. He is not just passively overcome by sin but actively and willingly uses his strength, ability, and gifts to sin.
The truth, then is that men are very wicked, much more wicked than they themselves would ever admit. Nor is this wickedness incidental, but deeply imbedded in what a man is, what we call his "nature." In other words, his depravity is not something he has learned or that is the result of his environment, but he is by his nature wicked. He does not just do evil but is evil. He is conceived and born a sinner...
We use this language to emphasize that man is so wicked that he lacks any good, even the ability to do good or the desire to do what is good. This emphasis is necessary because of the many ways in which the doctrine of total depravity is denied. Usually three things are meant by the word "total":
a. Total depravity means, first of all, that the totality of the human race is depraved. There is no one, not even a newborn infant, who is not corrupt and wicked. Nor are there any primitive people who still live in some kind of innocence. All are depraved.
b. Total depravity means also that every part of man's existence is filled with wickedness. In other words, not only his actions are wicked, but his speech, his thoughts, his motives, his wishes, his mind, his soul, his spirit—everything he is and does, inwardly and outwardly—are wicked. He cannot do, desire, or even understand what is good.
c. Total depravity also means that every part of man's existence is totally wicked. That is to say, his mind is not partly wicked and partly good, but completely wicked. The same is true of every other part of his existence, especially of his will. His will, too, is in bondage, so that he cannot even want what is good, nor is there any desire for good to be found in his life and thoughts.