Attacking Syria is not an act of self-defense. Syria has not attacked the United States. Nor is Syria a danger to the US.
Syria has not attacked Israel and has not even responded to numerous Israeli bombings of its soil.
In addition the US attacking Syria would also not amount to defending „democracy“ for the syrian army is not fighting against any democratic state or entity.

What we know is that an attack with poisonous gas killed around 350 people in the early hours of August, 21st.
The much quoted „Syrian Observatory for Human Rights“ and the „Doctors without borders“ both spoke of 350 dead. There is a gap of 1100 dead to the approximately 1450 victims John Kerry mentioned.
We don´t know who committed the attack. We also don´t know which gas was used. Judging from the symptoms it is rather unlikely that a „classic“ chemical weapon such as Sarin has been used:
http://strongpointsecurity.co.uk/site/wp-content/uploads/2013/08/Revised-Thoughts-on-Damascus.pdf

While the US says that an attack on Syria would only be limited and directed against military targets earlier cases of  so called „surgical strikes“ or „precision attacks“ have managed to hit civilians with alarming regularity.
The prospect of incoming Tomahawks and cruise missiles has led many Syrians to flee their houses in panic and head towards neighbouring countries.
Any decision that transforms thousands of ordinary civilians to fugitives forcing them to live in uncertainty regarding their houses, their abandoned belongings, their jobs, their childrens school…is highly irreponsible and all but a necessary „humanitarian intervention“.

So far the US government has talked a lot about solid evidence but brought forward none. After days of building up tension and expectations by announcing the upcoming presentation of clear proof against the syrian government, a 4pages PDF file supposed to be full of damning facts contained nothing but a mess of assumptions and platitudes. Kerrys „evidence“ was actually a confession of failure, the evidence of no evidence.
Based on such (non-)facts and „evidence“ no US court would convict the defendant.
One of the main points in the paper meant to „prove“ that only the syrian government could have perpetrated the crime was the claim that the rebels have no chemical weapons. Something the CIA itself implicitly refutes:

„Al-Qa’ida and associated extremist groups have a wide variety of potential agents and delivery means to choose from for chemical, biological, radiological, or nuclear (CBRN) attacks…however, most attacks by the group—and especially by associated extremists—probably will be small scale, incorporating relatively crude delivery means and easily produced or obtained chemicals, toxins, or radiological substances…Analysis of an al-Qa’ida document recovered in Afghanistan in summer 2002 indicates the group has crude procedures for making mustard agent, sarin, and VX.“
https://www.cia.gov/library/reports/general-reports-1/terrorist_cbrn/terrorist_CBRN.htm

The likelihood of an attack on Syria causing catastrophic consequences is high. Here some scenarios:
– If the syrian government or the syrian president are indeed „insane“ or „delusional“ they could fire chemical missiles at Israel once they feel desperate, humiliated and cornered
– The syrian army is fighting mostly the same people, the US uses to call Al-Qaida and subject to drone attacks elsewhere:
http://www.independent.co.uk/voices/comment/does-obama-know-hes-fighting-on-alqaidas-side-8786680.html

The Nusra front, by far the most active and effective rebel faction fighting the syrian army has been declared a terroristorganization by the state department. In addition there are other islamist Jihadi groups raising the same Al Qaida banner assisting the Nusra fighters:
http://media.economist.com/sites/default/files/imagecache/full-width/images/2013/05/blogs/graphic-detail/20130518_gdc631.png

The allegedly secular „Free Syrian Army“ hardly exists anymore:
http://www.joshualandis.com/blog/the-free-syrian-army-doesnt-exist/

– In Iran a new, more moderate president is elected who seems to be willing to adopt a more friendly policy and improve ties with the United States. Attacking Syria would make it very hard for the new Iranian government to not take position
– A further strengthening of the syrian-iraqi Al-Qaida branch „Islamic State of Iraq and Syria“ by weakening Assad would pose an increased threat to the already fragile Iraqi state. The conflict could spill pver even more to Iraq and Lebanon. After many years of relative calm there are almost weekly bombings and skirmishes leaving hundreds of dead every month. In Iraq the AQI (Al Qaeda in Iraq) who backs the syrian rebels has intensified (suicide) bombings of market places, mosques, Cafes and even funerals killing more than 1000 people, most of them Shia muslims.

The american congress should vote against an attack on Syria. The attack would only bring further suffering to the syrian people and strengthen and embolden forces our media and politicians would call terrorists if they were fighting the US or Israel.