Three young medical students were snapping photographs of a scene of devastation on Monday: five stories of mint-green, concrete rubble that until Israel’s war with Hamas began had been their science lab.

“They hit my future with a rocket,” said Muhammad Baroud, one of the students at the Islamic University in Gaza City. “This is a university. What does it have to do with war?”

As Gazans surveyed the destruction of the city on Monday, one question kept arising: Why had civilian institutions been hit? At lunch tables and in coffee shops, people listed the targets: the Ministry of Justice, Parliament, the central police station, the fire station, Islamic University.

Israel argues that those institutions help funnel money, supplies and people to Hamas, which it considers a terrorist organization, and for that reason they are legitimate targets in Israel’s efforts to weaken the group.

“The civilian infrastructure provides the administrative, logistical, human resources and funding structure, which supports Hamas’s entire military effort,” said Capt. Benjamin Rutland, a spokesman for the Israeli military.

But many Gazans say that the strikes, which left gaping holes and giant piles of rubble in the center of the city, felt more like an attack on them as a society, as the leveling of the institutions was a direct hit against the rule of law and the structure of the state.

“The war was not against Hamas,” said Rahmi el-Kheldi, the owner of a flower shop in central Gaza. “It was against me, my shop and my city.”

He added, “Their aim was chaos, to disrupt society.”

For Mr. Baroud and his friends, the bombing of the science lab building, which happened in the early days of the Israeli offensive, was a frontal attack on their future. The university is prestigious, and they said they worked hard to get there. It is one of the best medical schools in the region, and Israel recognizes its degrees.

“Are we going to study in a tent?” asked Mr. Baroud’s friend, Ahmed.

But the question of what is a legitimate military target can be tricky. An Israeli military official, citing intelligence reports and speaking on the condition of anonymity because of military rules, said that the labs functioned as research and development facilities for Hamas’s homemade Qassam rockets, and that a large number of people at the university were involved. The attack was precise, the official said, with the science building’s being the only one that took a direct hit.

Those interviewed about the university on Monday strongly denied Israel’s claim. Fakhr Abu Awad, a professor of chemistry at Islamic University, said that the school was a cross section of Gazan society, and that Hamas, popular in Gaza, was similarly represented there. But supporting Hamas, Mr. Abu Awad said, is a far cry from taking part in its military activities, and he dismissed the Israeli claim as almost too insulting to answer.

“This is an academic institution, and it’s not acceptable,” said Mkhaimar Abusada, assistant professor of political science at Al-Azhar University-Gaza, referring to Islamic University. “Even though Hamas was launching missiles against Israel, it does not mean Israel has the right to bomb civilian infrastructure.”

Ahmed said, “The Israelis say there are weapons, but I’ve been studying here and I never saw any.”

The issue, in part, is about the very nature of Hamas. Gazans say that there is a range of relationships people have with the group, starting with sympathizer and ending with rocket launcher or suicide bomber. Just because someone likes Hamas does not mean that that person is necessarily working for the group, Gazans say.

“We are sympathizers, but we have nothing to do with launching rockets,” said Adam Ghabin, 21, a firefighter at Gaza City’s main fire station, which has two giant craters in its complex from bombings. Hamas martyr posters were taped to the walls.

But many civilian jobs, like that of a police officer, for example, fall into gray areas.

As armed, uniformed members of a state that is run by Hamas, Israel argues, the police are legitimate targets. Abu Aymad, 52, who has worked in Gaza’s police force as a prison guard since 1994, long before Hamas came to power, disagrees.

“The police is a civil institution,” he said outside the pile of rubble that once was Gaza City’s central police station. “It serves the people, not the parties.”

He points to his smoking habit as evidence that he is not a hard-core supporter of Hamas, which takes a strong Islamic line and disapproves of drinking and smoking. An attack on the police, he said, was a strike at the heart of a state ruled by law.

“They hit the police building because they wanted to create anarchy,” he said, his mustache yellow from smoking.

A student at Islamic University who was visiting Mr. Kheldi’s flower shop said, “Just because Hamas is present in civil institutions doesn’t mean they’re not legitimate institutions.”

Mr. Kheldi, a supporter of Fatah, Hamas’s political rival, said that much of the police force was loyal to Hamas, and that even traffic police officers could help by monitoring the streets and informing the group.

Still, the destruction felt profound and shocked even the most hardened observers.

“It’s something very massive, beyond imagination,” Mr. Abusada said.

Abdel Hamid Khdair, a security guard at the Parliament building, which on Monday looked like a giant robot, its bare skeleton buckled but still standing, said: “Everyone was hit by Israel this time. Education, health, life. Everything is paralyzed.”

An Israeli official responded by saying, “Given the extensive nature of the Hamas infiltration of the civilian infrastructure,” such as booby-trap bombs, “damage was unavoidable.”

Mr. Baroud was unconvinced.

“I want to ask the Israelis,” he said, “why did you do this to us?”

Palestinians see the war as yet another attack on their national identity, Mr. Kheldi said. Though Israel was trying to drain support for Hamas, he said, violence will make Palestinians only more defensive.

“They think the more they kill, the more we lose our will,” he said. “But it’s the opposite.”

He continued: “Now, when I see a rocket fly, I hope it hits a bus. Not because I want to kill kids, but because they’ve killed so many of ours.”