Dear Rachel,

Thank you for your question. I'm sorry that it has taken me a few days to find the time to respond.

The subject of usury is often cited as "evidence" that the Church has amended past doctrine to fit society's norms in a given historical context. (Usually by the folks promoting the ordination of women, birth control etc.) Once again, nothing could be further from the truth.

Throughout history and to the present time, the church has condemned the practice of usury: St Ambrose, St Jerome, St Augustine and Pope Leo all considered it to be sinful, a social injustice to the poor.

The second Lateran council spoke in 1139:

We condemn that practice accounted despicable and blameworthy by divine and human laws, denounced by Scripture in the Old and New Testaments, namely, the ferocious greed of usurers; and we sever them from every comfort of the Church, forbidding any archbishop or bishop, or an abbot of any order whatever or anyone in clerical orders, to dare to receive usurers, unless they do so with extreme caution; but let them be held infamous throughout their whole lives and, unless they repent, be deprived of a Christian burial.

Similarly, the canon 25 of the third Lateran council (1179) says:

 "Nearly everywhere the crime of usury has become so firmly rooted that many, omitting other business, practice usury as if it were permitted and in no way observe how it is forbidden in both the Old and New Testament. We therefore declare that notorious usurers should not be admitted to communion of the altar or receive Christian burial if they die in this sin." And Canon 29 of the Council of Vienne (1311) says, "If indeed someone has fallen into the error of presuming to affirm pertinaciously that the practice of usury is not sinful, we decree that he is to be punished as a heretic."

The Catechism of the Catholic Church makes the following reference to usurious behaviour:

The acceptance by human society of murderous famines, without efforts to remedy them, is a scandalous injustice and a grave offense. Those whose usurious and avaricious dealings lead to the hunger and death of their brethren in the human family indirectly commit homicide, which is imputable to them. (CCC 2269)

Now let us examine how the foregoing relates to present practices. Do you have an interest bearing savings account? A mortgage? In my Diocese, all parishes are required to deposit excess cash into a revolving fund pool which bears a guaranteed rate of interest and makes fixed rate loans to the member parishes. How to reconcile this? The solution lies in how the Church looks at the definition of usury.

Let's look at the Biblical background first: Ex 22:25 and Lv 25:35-38 instruct that the poor should receive interest-free loans. Dt 23:19-21 commands no interest loans to other Jews, but allows interest to be charged to foreigners. In the Wisdom and Prophetic books, the greed of the rich is condemned, which oppresses the poor by exacting interest which they can't afford.

In the NT we have several instances where the faithful are exhorted to be compassionate and generous in lending (Mt 5:42, Lk 6:34). In contrast to which stands the parable of the Talents (Mt 25:27): "All the more reason to deposit my money with the bankers, so that on my return I could have had it back with interest."

Clearly scriptures and even our Lord himself do not see the charging of interest to be, in itself, categorically immoral.

Rather, the Church Fathers were concerned with the oppression of the poor, or as we would say today, the social justice aspect of usury. The Church is in the business of sheparding the flock, it always has and always will condemn usury, as contrary to charity and mercy, but it doesn't teach (and never has)  that any charge above the loan principal is automaticaly immoral. 

One more thing to consider is the question of doctrinal development. Money was not seen as a vehicle of investment until the 8th or 9th century, it was rather looked upon as a consumable to be bartered. Monetary loans were most often made for a short term, consumable need and so the concept of interest was seen as "charging twice". St Thomas Aquinas wrote:

To take usury for money lent is unjust in itself, because this is to sell what does not exist, and this evidently leads to inequality, which is contrary to justice. In order to make this evident, we must observe that there are certain things the use of which consists in their consumption: Thus we consume wine when we use it for drink and we consume wheat when we use it for food. Wherefore in such like things the use of the thing must not be reckoned apart from the thing itself, and whoever is granted the use of the thing is granted the thing itself and for this reason, to lend things of this kind is to transfer the ownership. Accordingly if a man wanted to sell wine separately from the use of the wine, he would be selling the same thing twice, or he would be selling what does not exist, wherefore he would evidently commit a sin of injustice. In like manner he commits an injustice who lends wine or wheat, and asks for double payment, viz. one, the return of the thing in equal measure, the other, the price of the use, which is called usury. (ST II-II.78.1)

Not until the scholastic age did money become a more common medium of investment.

The Church does respond to changing cultural and exterior conditions of the secular world, and so, doctrinal teaching does undergo development, however this will not and has not ever negated any teaching of the magisterium related to faith and morals. You are Peter.....and the gates of hell shall not prevail against it.

Hope this helps, God bless,
Brian