Septem Artes Liberales, by Herrad of Landsberg (1180 AD).

The classical liberal arts are seven in number and were the basic skills believed necessary for success in philosophical and theological studies. We can examine them using the 12th century monastery painting above. 

Philosophy

In the center of the painting above, we find lady Philosophy, to whom all the arts give service.  She sits as queen of the arts, with the philosophers Socrates and Plato under her feet.  In the upper right corner, we read,

"Seven fountains of wisdom flow from Philosophy which are called the seven liberal arts.  The Holy Spirit is the inventor of the seven liberal arts, which are: Grammar, Rhetoric, Dialectic, Music, Arithmetic, Geometry, Astronomy."

It is important to note that the seven liberal arts were held to be invented by the Holy Spirit.  It seems unlikely that the Holy Spirit would invent an educational system that was inferior to that invented by modern "expert".  The changes in education that took place in the early 20th century were errors, not improvements.  Until we restore true education, we will not cease to reproduce the results.  We will consider the seven liberal arts surrounding philosophy beginning at the top.

grammar

Grammar was called by the ancients the Janua Artium, the "gateway of the arts".  Grammar holds a book and a rod (scopae) probably for punishing young students.  Above Grammar, we read,

Per me quivis discit, vox, littera, syllaba quid est..

By me does anyone learn what is the voice, the letter and the syllable.

rhetoric

Moving clockwise from Grammar, we find Rhetoric, holding a tablet and stilus.  Rhetoric is the art of finding the means of persuading an audience.  Above her we read,

Causarum vires per me, rhetor alme, requires.

By me, kind Rhetorician, you will seek the force of motives/cases.

St. Augustine addressed the importance of Rhetoric best:

"Who will dare to say that truth is to take its stand unarmed against falsehood.  Since the faculty of eloquence is available for both sides...why do not good men study to engage it on the side of truth?"      

                                         -On Christian Doctrine, book IV

dialectic

Next we find Dialectic, or Logic holding a dog's head.  Some believe the dog to be used in opposition to the wolf typically associated with heresy.  Above Dialectic it is written

Argumenta sino concurrere more canino.

I allow arguments to battle in the manner of a dog.

music

Fourth is Music, playing the cithara, lyre and organistrum.  Above her, we read,

Musica sum late doctrix artis variatae.

I am Music far and wide the teacher of the arts of variation.

arithmetic

Fourth is Arithmetic, the art of counting objects at rest.  Here she is seen counting beads on a rope.  Her banner reads,

Ex numeris consto, quorum discrimina monstro.

From the numbers I exist, of which I teach the differences.

geometry

Sixth is Geometry, the art of measuring objects at rest rightly.  Geometry is seen measuring the earth with a compass.  Over Geometry we read,

Terrae mensuras per multas dirigo curas.

By many pains, I direct the measurements of the earth.

astronomy

Last is Astronomy, holding a bushel basket and numbering the stars.  The art of astronomy considers the relation between numbers and the laws of motion.  Above Astronomy we read,

Ex astris nomen traho, per quae discitur omen.

I draw my name from the starts, by which the omen is learned.

Lastly, what makes the classical liberal arts Christian is the spirit in which St. Augustine advised that they be pursued:

"It is well to warn studious and able young men, who fear God and are seeking for happiness in life, not to venture heedlessly upon the branches of learning beyond the pale of the Church of Christ as if these could secure for them the happiness they seek."