Modesty in dress, tzniut, is an important value in Judaism. What does it actually mean?
The term commonly used to translate tzniut is ‘modesty’, which refers to someone who is humble versus one who is arrogant. This is not an accurate translation of the word tzniut which means to keep something intimate and private, away from the public glare, and refers to Judaism’s requirement to cover the body.
Even in a modern world – it sounds so outmoded…
G-d gave us the Torah for all times and all places. But this points to the major challenge.
Which is…
One of the most powerful influences over a person is the society around them. It is human nature to look around and see what others are doing to work out the appropriate way to behave. Regarding tzniut, there are certain eternal values of Judaism at stake. One value is human dignity. For a person to be dignified at all times they need to dress appropriately. Tzniut is about the beauty of dignity, about Jewish women living as royalty without debasing themselves through crude externalities.  And the second value here is the sanctity of sexuality.
How can sexuality be holy?
The Torah views sexuality as something created by G-d, which has the potential for great holiness if channelled in context of the sanctity and holiness of a marriage. The very word for marriage is ‘kedushin’, which comes from the word holiness. We say under the chuppah ‘harei at mekudeshet li’ – which also means that you are designated specially for me. This couple become designated only for each other. So the holiness is only when it is in the intimacy, privacy and commitment ofmarriage. When it is outside of that, sexuality can become a very destructive force in the world, the very opposite of sanctity.
But how does the way we dress become a destructive force?
The guiding philosophy of the laws of modest dress is the protection and shielding of sexuality from public glare and a loving relationship is very private and personal.  It is about an intimacy that only a husband and wife can share.  If exposed in public light, it is not about the husband and wife anymore; it becomes part of the public domain.
But what is the problem with this?
It makes sexuality about physical desire alone, and not about a loving relationship. Sexuality is a very powerful force in human nature and if not contained in a marriage, it becomes a force for mere self-gratification. It becomes about taking, not giving. About objectifying other people. All too often, a person is seen as an object of sexuality rather than for who they are. And it can lead to the very destruction of relationships. If sexuality is shared between people who are not married, or between married people and other people, or any other context other than marriage, it becomes a cause for destruction, and unhappiness.  Ironically, through the restrictions of the Torah we become liberated to experience real happiness and meaning.  This makes sense because the Torah is after all G-d’s plan for how to live our best life.
Can’t everything in life be used for good as well as evil?
Yes, this is a general philosophy in Judaism – everything that G-d has created in this world has a potential for good and for evil. And this is what it means for us as humans to have free choice.
How so?
The Rambam writes that the main difference between humans and animals is the choice between good and evil – free choice. So yes, anything can be looked at in terms of good and bad. Take money. When used for good, it can be enormously positive – it can feed the poor, support Torah education, and help others retain their dignity. But it can also become enormously destructive, leading people to destroy their lives, through greed, unethical behaviour, and stress. Everything has the power to destroy or to be used for good, and that is the choice placed before us. Look at the desire to eat. It can be positive – a person needs nutrition and we can see what happens when people are malnourished. On the other hand, when unconstrained, it too can destroy a person – through greed, gluttony, and the many illnesses caused by obesity and excess.
But we can still enjoy the physical, surely?
A Torah way of life actually helps us to be truly happy and to enjoy the physical in a much deeper way, in a way that gives us emotional and spiritual fulfilment at the same time. The general guiding rule is this – when these physical desires are channelled within the framework of Torah values, and channelled not only to take for oneself but also to give to others, then that is generally going to be the path of goodness. When they are outside of these bounds, and used for selfish purposes, then that just leaves a person feeling emotionally empty and without spiritual meaning.
But why is this rule specifically related to dress so important?
Because it is actually about creating a society of holiness and dignity. It is about  cherishing the privacy of marriage and it is about being treated as a human being and not as an object of gratification. It is about creating a life of true and deep contentment through real love and intimacy with holiness.
Does tzniut extend to other areas of life?
It is also about what we look at, and here is where we need to protect our children, who through TV and internet are exposed to imagery which they do not have the intellectual and emotional capabilities to assimilate. Researchers are looking into the correlation of the effects of child abuse and the exposure of children to this kind of graphic imagery and finding similarities. The Torah says that it is even damaging for adults, as it creates impressions that negatively impacts on relationships and marriages. The lack of modesty and damages society by damaging the relationships that are fundamental to it, and by undermining human dignity, and in the end is a threat to our happiness.